Complete with back-up signers! (not a spelling error!)

One of the best ways to learn any language is to immerse yourself in it. With American Sign Language (ASL), that's a bit more difficult to do than for the more standard spoken languages taught in schools. But if you search "ASL song" on YouTube, you'll find hundreds, if not thousands, of popular songs signed with the song as audio track. Watch just a few and you'll be able to recognize way more words than you would in the same amount of time studying vocabulary from books.

If you know Jonathan Coulton's song "First of May," I urge you to visit this YouTube video. (WARNING: NSFW if you don't have headphones, or if your co-workers know American Sign Language.)

ETA: The guy who does the video has several more signed songs--not all are Jonathan Coulton.

EATA: Holy *crap*. Marilyn Manson's This Is the New Shit in a signed/performance video performance with... well, just go watch it. The warning here is that it may freak some viewers out, but I think it's pure genius. You're not going to get signs for all the words so much as an interpretation of the song that includes ASL. But... whoa.