#4-40 nuts & bolt/screws. Bought a couple boxes of different lenghts from www.boltdepot.com after cleaning out the local hardware store (not home depot, they don't go that small).
Home Depot does have bags of stick-on cable tie holders tho.
Nylon spacers from www.pololu.com, bought couple bags of different lengths.
Also crimp housings and terminated wires.
Male terminations for plugging into female headers, female terminations for sliding onto 0.025" square pins.
Have used a lot of both. Bags of 50 wires, very handy.
This place also has lots of those kinds of parts
also sockets, socket strips, header strips.
Stepdrill/unibit drill very handy for making holes in plastic, does not dig in & rip up the plastic.
I have a couple of different sizes.