Recommended USB control pads?

I play emulators on my mac and I can't seem to find a decent controller. The ones I've used (Gravis and recoil) work ok, but the d-pad is very slippery and moves up/left or up/right when I just want to go right or left. I've tried all the settings and it doesn't help.

Can anybody point me to a link for a good USB pad that
a.) has good digital control (press right or left and go right or left)
b.) doesn't cost a fortune
c.) is plug and play - doesn't require extra drivers

Do most pads that say they only work on pcs work on macs too? I thought USB was all plug n play and universal.

Does anybody know of a link that sells Playstation 2 ---> USB mac converters? I've tried all the import shops and ebay, but no luck.

Thx in advance.