Originally Posted by NateST
Depending on the router you have you're going to want one thats runs the same speeds presumably so you can get the most out of your conection. If you have an N150 router there is no need to get an N300 adapter, I've sold a bunch (Officemax) and find that even the cheapies work quite well, I myself have just an old one that i've had around for ~5 years, Linksys G Adapter for our WRTG54 thats also quite old. I would suggest to buy an N150 adapter if you have an 150 router, 300 adapter for 300 router etc, any major brand will probably do (Linksys, Netgear, Belkin, D-Link) etc.
Well it also depends on the model, some wifi cards from any of those companies are crap while some are awesome, you have to do some review skimming in order to find the right one.
I did a quick search and came up with this one as being cheap and half decent:
But personally I use a WRT54G with DD-WRT as a bridge and it works beautifully, there is no extra latency and it never cuts out. Its almost as good as wire, I can even have three or four devices connected to it and it will still work without issue. If you can get your hands on one of these, I really recommend it.