A USB interface will do (as long as it's 2 or more channels). Other popular options include Firewire and PCI.
As for which brand or model, you'll have to ask around and do your research. Depends a lot on your setup, your goals, and of course your budget.
Personally I use a Presonus Firebox (Firewire). Average cost is about 300bucks and so far has been a very reliable unit with a good sound.