At ASL University (Lifeprint.com), a variety of resources are available for learning sign language free, for teachers as well as students. These are provided n text format, animated graphics, and a few embedded videos. Lessons are provided that include vocabulary words, practice tests and a checklist of objectives. A great place to start is Basic ASL: The First 100 Words.
While the website itself is pretty basic and pared down from a graphics perspective, it is rich in resources - most of which are available on CD in the bookstore for a relatively small fee.
Apples4TheTeacher.com has a nifty fingerspelling translator. Type up to 30 characters in the text box, press the translate button, and you'll now see your word or phrase translated into the ASL hand signs. Fingerspelling flash cards and other activities for kids are also available, and are a great way to mastering the sign language alphabet.
At SigningSavvy.com, you can choose from literally thousands of words that have been arranged in alphabetical order, click on their link, and watch a small embedded video of a person using the coordinating sign for the word you selected. Register here (also free!) and you'll have access to larger video screen, create a list of signs you wish to learn or review, use their "browse signs" categories to learn a group of related signs, and more. There's even an interactive map of the U.S. that allows you to see the sign for any state you choose.