I second Stealthtech. Any 24-bit 44.1 - 96kHz sound card should do it.
Just make sure that the drivers that come with the card support your application (i.e. Logic, Cakewalk, etc.) and that the drivers support your opperating system.
Here are a few suggestions:
Delta 1010
MOTU 2408mkIII
MOTU 24i
Aardvark
RME
MOTU 828mkII (Firewire)
MOTU 896 (Firewire)
Just make sure that you have some kind of pre-amps for the microphones. The Delta 1010, MOTU 2408mkIII, 24i, Aardvark, and RME do NOT have pre-amps. This means that when you plug your microphones into it, there will be nothing to boost the signal up to "line level" so that you can hear/record it.
You would still need something with pre-amps. Like maybe
the Focusrite OctoPre. It has REALLY good pre-amps for the price. You could also just buy the smallest Mackie mixer you can find and use it's pre-amps. I'd stay away from Behringer mixers. But that is a personal opinion.
The 896 from MOTU is a firewire unit so you have to have Firewire connectivity on your computer. But it has pre-amps built in. There are other units with pre-amps. Some have more than others. Some have better than others. Take a look around and narrow your choices down and then we can discuss your specific needs.