Avoid the Voodoo cards. The company that made them - 3Dfx - is essentially gone. Nvidia purchased 3Dfx's carcass in order to ensure they had a lock on the high-end GPU market. While you can find hobbiests that might be able to help you with 3Dfx gear, you will not find official support for any 3Dfx card anymore.
Any of the Nvidia "GeForce" chipsets are a good choice. Most manufacturers that use Nvidia's chipsets stick to the reference design for the most part so one manufacturer's products are all fairly similar when compared to another's using the same Nvidia chipset. As long as the Nvidia GeForce chipset on the card you are buying has either a 2 or a 3 in it you'll be fine. You can pick up a GeForce2 MX for next to nothing and the GeForce3 isn't a bad buy either.
Be careful, on some older motherboards newer cards that require a AGP 2.0 slot will give you nice BSOD's in DirectX games. On a Abit BE6-II, a Radeon 8500 nada, Generic Nvidia Ti-200 nada but a MX400 worked fine. It scores around a 2500 on 3DMark for around $70 bucks, not bad. The old Voodoo 3 is still a great card & drivers are still available at www.3dfxfiles.com
If you running XP bump the ram up to 256MB.
Hope your all are running the 27.42 Nvidia drivers, the 23.11 are trash.
The VOODOO 5500 go for around $50-100 on Ebay, yes drivers are available and yes its still a good card for gaming. But ultimately the Geforce4 ti4600 is the best out there for gaming, even though most games do not take advantage of its power.