Mr. Metric, which has great prices on (as you might have guessed) metric parts. They've even got M2 sizes. Various grades, etc. $6 flat rate shipping, and free shipping over $50. Example price: M3x8 stainless steel socket head screw (pictured), $.06 each in quantities of 101.
Update: I don't recommend KOVA fasteners from India, no matter how many times they leave spam in the comments below! Update: and Udehra too! Update: three times, Udehra stop it! And Indian Cutting Tools!