Amazon McMaster
Amazon Supply, looks like a McMaster competitor (via Gus Mueller). There’s free 2-day shipping with a $50 order (rather than the free slow shipping with a $25 order at regular Amazon), and it works with Amazon Prime. Many of the items that I looked at don’t seem to be in stock, however.
Looks like they rebranded smallparts.com, which has been an affiliate company for a while: http://news.ycombinator.org/item?id=3879976