I am fortunate to live in a community with a large south Asian population, so finding local saris is easy.

A few places online:
www.indiaplaza.com
www.radhasilk.com
www.reems.com

There are countless others!

There's a seller on eBay called evergreenen (Evergreen Enterprises) who also sells saris and salwar kameez at reasonable prices (relative to what you would expect in the States). I've ordered numerous things from this seller with no complaints. The best place to buy these outfits though is India.......ah, someday I'll get there!