Hi aml4
We might need a bit more detail in order to be able to help.
How many inputs/outputs are you looking for?
Can you use PCI cards or are you on a laptop?
Mac or PC?
What software are you using/would like to use?
There's a shedload of good cards out there (M-Audio, Echo, MOTU, Presonus, MBox to name a few) which have various configurations and may require specific computer environments/software to run with.
If we know what you're running and what wanting to do with your studio setup we can hopefully give you a few pointers to get you started.
Cheers!
Dags