A lot of the Lorex cameras seem to have audio; this one in particular would probably suit your needs:
http://lorexstore.lorextechnology.com/product.aspx?id=2027
If you're looking for an IP cam and not analog, then maybe even something like this:
http://www.frys.com/product/6483512?site=sr:SEARCH:MAIN_RSLT_PG
I learned 2 things from my baby-cam... 1) quality isn't really that important; it doesn't take that much to know what's going on. and 2) two-way audio is really handy.
I actually used audio only for both my kids at first; I upgraded to video when my oldest was at the age of trying to climb out, and in preparation for her getting a regular bed, so I could keep an eye on her. I use the audio all the time to talk to her.
For my needs, I use a wireless digital baby monitor system from Summer; kinda low-tech for this place, but it works for my needs... and when we travel we take it with us for the hotel rooms even. The image quality is really sub-par, but the handheld is very convenient and can control the PTZ, and has the two-way audio. At night, the tiny 3.5" screen would be useless to me, so it's plugged into a dedicated 24" LCD TV in the bedroom that I can see well enough without my glasses/contacts. I've considered plugging it into a video server as well so I can get IP access as well.