What kind of SSD is compatible with the 2010 Unibody MacBook?
You're looking for any 2.5" SATA drive. I'm not sure if the MacBooks came with SATA 3 (6 Gb/s) or SATA 2 (3 Gb/s), so you should match whichever the installed drive is. (There's no harm in putting a SATA 3 drive in a machine that only supports SATA 2, you just won't get the speed and you'll pay more.) You should be careful of 12.5mm height drives - they won't fit in some Macs. Anything smaller should be fine.

Some references: 


mid-2010 MacBook manual – look in Chapter 3 for specifics on hard drive replacement
iFixit's MacBook repair guide – has better pictures than Apple's manual (I think this is the right one)