Guitar Center has the TASCAM DP-004 Pocket Studio on sale for $100. I picked one up a few days ago, and have had a chance to play around with it. Its a great, no-frills four track that reminds me of the easy, "instantly up-and-running" four track cassette recorders of the late 80's, early 90's. Records to an SD card... you can pop the card out and put it in your computer to transfer the .wav file. Its quite small, very well laid out, and runs on batteries (you can buy a power adapter as well).
I do love how quickly I can plug in my BOSS drum machine/guitar effects unit and record. The unit also has some very good multi-tracking features, like "bounce" which essentially allows you to bounce all four tracks to two tracks, add two more, bounce, and repeat until your head explodes.
If you're looking for a small, easy to use unit to rough out song ideas, this thing is worth checking out. I couldn't say no at $100.