If your only dealing with a 1-2 bdrm apt. 802.11 b/g should be fine. I would recommend one like this
I agree with Dachew that you should have one with an external wired antennae it helps with reception. This one is a little expensive but it supports WPA encryption and AES (Advanced Encryption Standard) which is important in an apartment setting. There are less expensive models anything from Netgear, Dlink, linksys, will serve you well. I personally use a Netgear adapter on my FAH machine.
Edit: Since you have a router make sure The advanced security is compatible, otherwise its pointless unless you get another router.
Edited by Sneakycyber, 20 February 2008 - 05:10 PM.