MacBooks take 2.5" drives with a maximum height of 9.5 mm.
S-ATA 3.0 Gbps (also known as SATA II) is backwards compatible, so drives with the S-ATA 3.0 Gbps interface will work with computers with an S-ATA 1.5 Gbps interface.
The current maximum disk space is 500GB (465 usable GB, unless you have Snow Leopard, which uses the base 10 for showing your disk space) for drives that will be suitable for the MacBook.