I used the D-Link one that I posted above, but I screwed up the firmware so I guess I would have to recommend the Linksys wireless router:
LINKSYS WRT54G IEEE 802.11b/g, 802.3 Wireless-G Broadband Router up to 54Mbps Data Rates 1x10/100M WAN; 4x10/100M LAN
Do you have a laptop as one of the PCs for your network? They need a different type of wireless adapter card. Here's the one for your desktop PC. Just buy two of these if you want to connect two desktop computers together. It's better to get the Linksys ones to match so there will be no incompatibility issue:
LINKSYS WMP54G IEEE 802.11b/g PCI Wireless Adapter up to 54Mbps Data Rates 64/128-Bit WEP
If you want to go cheaper, you can get the D-Link wireless router to go with this wireless adapter:
D-Link DWL-G510 IEEE 802.11b/g 32bit PCI2.2 Wireless Adapter up to 54Mbps Data Rates 64/128-Bit WEP
Honestly, D-Link looks really good. It's much cheaper, and they are very very reliable. I just threw in the Linksys so you can compare the two top wireless devices to use.
I'm not sure what the difference are between the USB adapters and the PCI ones. I'm so use to the PCI one that I never thought about the USB version. The PCI always works for me without a single problem.