I have
this Zonet b/g adapter, and it is strong. Have had it for a couple of years now, and it works great in both Windows and Linux. Great price for it now as well. Don't know about any USB N adapters, but I have this
Asus PCIe adapter. The USB adapter has better range, though.
http://www.newegg.com/Product/Product.aspx?Item=N82E16833130111
http://www.newegg.com/Product/Product.aspx?Item=N82E16833320048