I've been reading on the PS3 forums that 802.11 USB adaptors don't work yet, Sony is working on a update that will allow to use most common brands. For now if you want to have a wireless connection you need a 802.11 bridge. You can reconfigure most routers to be a wireless bridge if you have an extra router or you can buy something like this - WGA54G
On Amazon that thing is kinda expensive so it's probably cheaper to buy a netgear or linksys router and reconfigure it as a bridge.
I just checked ebay and they are going for like $50