That's an ok thread, but I'll just answer the question since that thread doesn't say what it needs to. Get either a Netgear or a Kingston. They are the best priced for quality. Just make sure you get the right type of card...PCI or ISA. If you go PCI, I would suggest a netgear 10/100...They're good because they're made by Nortel Networks(formerly known as Bay Networks)...Circuit City has pretty good prices on these. Kingston is good because they run REALTEK chipsets which test reliably for compatibility. That's it.
EDIT: Oh yeah, not quite "it", don't pay over $30 or you're getting ripped...