Unless it specifically says it's NOT Mac-compatible, the key specs to look for are "OHCI" & "EHCI" compliance......the majority of cards meeting those 2 specs will work in most macs running OS X, since the drivers, extensions and protocols are built into the core of the OS.
I would suggest skipping the ebay bargin bin/peecee crapola cards and just flop down about $15 for a brand new Belkin or D-Link card. No worries that way plus warranty & return possibilities too.....they are available just about everywhere, wallyworld, bustbuy, & most office supply stores too
