What do they have? Well...almost everything! Seriously. Here's a very small sample:
Springs, tweezers, drill bits, brass tubing, music wire, needle-nose pliers, calipers, universal joints, cam follower bearings, WD-40, shoulder washers, gears, wood screws, pin vises, worm gears, brazing torches, cyanoacrylate adhesives, ball bearings, pulleys, hole saws, router bits, machine screws, epoxy...and way, way more.
And, despite the name, it's NOT just small stuff. They sell full sized milling machines!
If you haven't already, I suggest you check out all the cool stuff available from SmallParts.com.