Amazon

As expected, you'll find many things you need on Amazon. Although searching Amazon itself will usually get you what you want, your shopping queries will often include lots of extraneous stuff that will give you a headache. Unless you're doing price comparisons, most of the Amazon stuff you order will be found more easily and directly on Amazon Supply (formerly Small Parts).

Of course, many things you find on Amazon you might also find at your local hardware store for less money. It's just that your local hardware store probably isn't globally available.

UPDATE 1/12/2013

Surprisingly, AmazonSupply no longer carries some FirePick parts. Specifically, M2 nuts are no longer available. This trend is concerning and implies that AmazonSupply is no longer a reliable supplier. Because of this, the preferred vendor for FirePick fasteners is now McMaster-Carr.