Are you looking for a standalone keyboard or one that you can (must) use with a computer?
The former is good for live performance or practice where a computer isn't around, but limits your functionality to the functionality of the keyboard itself.
The latter is great for more complicated mixing or composition, allows for easier recording, and allows you the flexibility of many good pieces of software.
I picked up the M-Audio Keystation Pro 88 on craiglist for $100 on craiglist about a year back, and it's served my needs and more, particularly when paired with powerful software like Cubase SX3.
M-AUDIO - Keystation Pro 88 - 88-Key Hammer-Action USB Bus-Powered Master MIDI Controller. The big caveat, however, is that you need a computer. Without a computer, a MIDI Controller is a big useless piece of plastic.
As for resources, I came across GMajor Music Theory when I was looking:
Free Piano Music! Level One
It was great because it has beginner through relatively complex compositions, but it provides the sheet music AND MIDI tracks for all the songs. It's great if you're a "learn by hearing and copying" or "learn by reading the music" person. I read the music, but it was occasionally good to play the MIDI to make sure I was doing it right.
I was a clarinet player long ago, but it took a while to remember.
Best of all, it's all free. He's got all sorts of other resources on that site too, including flash cards and stuff.