http://www.apparelsearch.com/World_Cloth��Personally, I use a lot of Polartec fabrics. I d also draw your attention to Siltex in Canada, which makes some very good cotton knits (their bare knits program). http://www.siltex.com/
The American fabric industry, though diminished, is still alive and producing multitudes of really fantastic fabrics. There are the major mills like Milliken and ITG (a combination of Burlington Industries, Cone Mills and other companies) and Mount Verrnon Regal. There are also very fine converters like Symphony-Pago Fabrics and Scher Fabrics in New York and jobbing (wholesaling companies) such as Magna Fabrics in New Jersey. There still are garment centers in both New York and LA with clusters of fabric jobbers and importers.Susan Powers publishes a great directory of resources The Resource Room And Guides NETwork at http://www.rrag.net