I second touch sensitive. I got a Casio wk-6500 and electric pedal (also important ). I can't play all the lower notes sometimes as it's a 61 key. It's not really inhibiting though. For the cost around $150 it's been really great to learn. I teach myself. If I may I recommend the book "more easy classics to moderns" by amsco music publications. If you like classical music it's a good starting book. Have fun learning!!
EDIT: Ok I respect other's opinions but Malcom that was a good keyboard you recommended but you should only speak for yourself when you call something else a toy (to me, my keyboard is no toy) or say others can't learn be self taught. For those who need more, youtube has many piano tutorials.
I play intermediate to advanced now after a little over 6 months of teaching myself. What I can play consists of: Bach's Air on the G string, Mozart's Sonata in C major, Chopin's prelude in E minor, Chopin's Raindrop, Chopins prelude in C minor, All of Bach's two part inventions, Schubert's Serenade, Pavane by Faure, Moonlight sonata by Beethoven, Elgar's Nimrod, in the process of learning Brahms' Symphony N. 3 third movement and First Arabesque by Debussy.
I use the Big Book of Classical music by Hal Leonard, and The Piano Bench of Classical Music Piano solo by Hal Leonard also. Plus 8notes.com to download free music.
AND TO SHEA: DON'T RECONSIDER THIS! I almost didn't begin...have so many other expenses that a keyboard didn't seem a necessity but I can't say how glad I am that I bought it and teach myself.
Oh and a scales, chords, arpeggios, and cadences book would be helpful to get also. I've used freecycle.org to get free lesson books.