Depends on what you're trying to do but the Carddeluxe from
Digital Audio Labs is pretty much the gold standard for $400. It's got 1/4" TRS stereo analog ins and outs, coaxial digital in and out, and supports 24/96 resolution. There's an optional bridge for digital AES and Toslink in and out. The card can also be ganged with additional cards to support more channels if necessary, it eats up alot of slots though.
If you need lots of ins and outs that might not be the card for you, or if you are looking to get a good editing software package with the card you might want to look elswhere. If your looking at doing just straight 2 channels of digital in and out then it's definately tops in it's class.
Echo's MIA and Gina systems are also very good for their low end stuff with multiple channels. The
Digidesign Digi 001 and M box come with the excellent Pro Tools LE software. Price is $1000 and $500 respectively. Kind of like buying a nice 21" monitor for $500 and it happens to come bundled with Photoshop. Could be overkill depending on what your using it for though.
-Bryn4ne