I suppose it really depends on your needs. If you have devices that can use wireless N then you would want a router and card that can both do that. If not you can go with a simple B/G wireless router.
If you don't need wireless N i would say a good bet would be the WRT54GL router by Linksys. It is a solid and reliable router. And i would go with an internal PCI wireless card over the USB style.
For wireless N you could look into something like the Rosewill RNX-N150RT that people seem to like.