I picked up a Canon MP560 for $100 from Staples, although you can find them online at Amazon for ~$60 now (and the upgraded models for ~$100).
It does automatic double-sided full-duplex printing, although I haven't used this feature yet. I think the best feature is that it's wireless, which means I can stick it in the opposite corner of my room and print to it from any computer on the network.
I've printed quite a few (~10-15) 4x6" pictures, and the quality is really good; the software doesn't report a decrease in tank levels yet. Oh yeah, all the tanks are individual (cyan, yellow, black, etc), so you can replace colors as needed instead of unnecessarily in bulk.
It is a scanner/copier/printer. I used the copier function on it to make a color copy of my passport to mail to a med school for a secondary, and the quality was fantastic, I was really impressed with it.
If you're looking to keep costs around $100, I highly recommend Canon's MP series, and shop online to save more.