For synonyms and antonyms:
The Literatures and Languages Library circulates print dictionaries. To find a monolingual Spanish dictionary, search the Online Catalog using the subject heading Spanish Language Dictionaries (Tips For Searching the Online Catalog). To find a Spanish/English dictionary, search the Online Catalog using the subject heading Spanish Language Dictionaries English.
An excellent way to build vocabulary is with Flashcard apps. To find the best ones, search online for "flashcard apps for language learning."
Beelinguapp is a free app exclusively for mobile devices and focuses on learning and practicing languages through reading. Within the app, you can listen and read stories in your language of choice, as well as follow along with its English translation. The side-by-side reading lets you check any vocabulary or sentences you don't quite understand. A variety of stories are available, including folk and fairy tales, mysteries, classics, and more.
Busuu is a free language learning app, providing access to lessons for twelve languages. The app uses the four main language concepts--reading, speaking, listening, and writing--and provides tailored lessons to aid in the learning process. Additionally, Busuu can connect users to native speakers, who can provide feedback on lessons, writings, and more. You can access the app on your computer or mobile device.
Drops is a free app that uses game-style mechanics to help you learn the language. The short, five minute lessons combine aesthetically pleasing word games with mnemonic devices. Drops also has a companion app, called Scripts, for learning character-based languages (or languages with a different writing system). While the basic app is free, there are also subscription options for more features. In addition to accessing the app on your device, you may also try it in your browser or download it to your computer.
Duolingo is a free language learning application that you can use on your computer or your mobile device. The app uses a game-like system to aid learning, letting you accumulate points for every correct answer, and even allowing you to compete against your friends. Small, short lessons make up a majority of Duolingo exercises, and the more you use the app, the more personalized your lessons become. There are a variety of languages available (with more being added every day), and no limit to how many you can learn! Best of all, you can practice your language skills wherever and whenever you want!
Babbel- This app is a paid "cousin" of Duolingo, though with 40 free lessons, it is a great option! Each class uses pictures to teach you vocabulary. Then the words you learned are used in related phrases and short dialogues adjusted to the the level you are at to build conversation skills. There are handy pop-ups that explain the most important grammatical points related to the learned material and if you are on a computer, they also include short cultural notes. You can also get separate packages devoted to improving specific skills such as grammar or vocabulary if you already have some experience with the language and only want to improve certain skills. Lastly, Babbel’s classes can be downloaded and kept offline for you to study.
Memrise is a free app designed to adapt to your needs as you learn a new language. It provides audio and video clips from native speakers to help with pronunciation, vocabulary building, and to grow your own speaking skills. Rather than focusing on grammar, Memrise prioritizes speaking confidently and learning how to communicate.
Mondly is a free app that uses course materials, chatbots, and augmented reality to aid the language learning process. They have 33 languages to choose from, and even allows you to learn a new language using your native language, instead of from English. This is relatively unique amongst language apps. The free version of Mondly gives you a daily lesson as well as seven other "Hello" lessons. Like Duolingo, Mondly awards you points for correct answers, even ranking you among other users in a friendly competition.
HelloTalk is a language learning app that focuses on learning through conversation. The app connects you to native speakers of the language you wish to learn, as well as allows you to teach them your native language as well. You can communicate with them through messages, voice recordings, video and voice calls, and even drawings. Additionally, the app provides language tools to help with pronunciation, translation, and tools to correct grammar or vocabulary errors within messages.
Like HelloTalk, Tandem is a language exchange app that uses communication with native speakers to help teach or aid in language acquisition. After joining Tandem, users may start conversations with native speakers of the language they wish to learn. Communication methods include text messages and voice and video calling/recording. Additionally, there are correction and translation tools for users, so they can correct grammar and vocabulary while chatting with one another.
HiNative- A Free App! This app makes learning correct pronunciation a breeze. It allows you to get the benefits of getting in touch with native speakers without the hassle of searching for an exchange partner or having to schedule a chat. Anything is up for question here; you can ask for translations, input on pronunciation, or advice on cultural norms. You can also help fellow learners with the knowledge of your own language(s)!
Great Ways to Learn Spanish Online
BBC Languages: Spanish--A comprehensive and lively collection of free audio and video courses for both beginners and intermediate learners.
Marco ELE -- An educational magazine that helps in learning Spanish as a second language. It has many great articles on the acquisition of language and analyzes resources and books that deal with learning languages.
About.com Spanish Language -- The website maintaned by About.com's Spanish Guide features a variety of language lessons, blog posts and several interactive elements including quizzes.
Spanish Blog: Language and Culture -- Great blog maintained by Transparent Language, a leader in language software. It has a staff of several writers and uses lessons, videos and even cultural anecdotes to help you learn grammar, vocabulary, pronunciation and more.
Destinos -- These videos teach speaking, listening and skills to understand Spanish through the telenovela or Spanish soap opera. There are dialects from Mexico, Spain, Argentina, and Puerto Rico that allows the listener to learn of the different Hispanic cultures. The videos are closed captioned in Spanish.
Coffeebreak Spanish--Excellent Spanish Podcast aimed primarily at beginning and early intermediate learners.
More Online Resources
FSI Language Courses -- Free Spanish audio courses taken from the courses designed by the U.S. Foreign Service Institute. It looks a bit stiff and formal but there are exercises, lessons and a wealth of audio files. There are many other languages available as well, not just Spanish.
Notes in Spanish and Notes From Spain --Sister sites that offer a wide variety of helpful resources for Spanish language and culture. NIS focuses on learning the Spanish language with a series of podcasts and NFS focuses cuisine, lifestyle and travel in Spain.
The Spanish Blog --A good resource put together by a Spanish teacher from Bilbao, Spain. Blog posts range from pronunciation guides to recipes and there are a wide variety of cultural and multimedia resources to help you learn and have fun at the same time.
Spanish Language and Culture--Maintained by a Spanish professor at Colby College, this website contains grammar exercises and some excellent activities which use songs, videos and even poems to help improve your Spanish.
Learn Spanish in Chile--Their Spanish Learning Area offers online quizes and games for practicing Spanish.
Study Spanish.com-- Features a wealth of tutorials for grammar, pronunciation, vocabulary and verbs available for free. Mostly for beginners and intermediate learners, with advanced lessons available if you sign up for their premium account.
Social Sites to Help Learn Spanish
Bitacoras and Meneame--If you've heard of the social bookmarking site Digg, these are two Spanish language equivalents. Search across thousands of blog posts and articles in Spanish, read the most popular posts on their homepage and vote for ones that you like. Great way to practice your reading skills and you might even meet some interesting new people. The two function almost exactly the same.
Tomisimo.org Forums and Wordreference.com Forums--Active language forums where you can post grammar questions to have them answered by native speakers, or you can learn by reading other threads or answering others yourself. You will almost always get replies by authoritative, knowledgable posters, which you can verify by seeing their native language, number of posts and reputation.