Things you might find helpful:
Magnetic tip screwdriver (or bolt driver with a swap-in magnet tip): available at any hardware store.
Needle-nose pliers (good for jumpers, pulling dropped screws out of recesses in cases): available at any hardware store.
Flashlight (for looking into dark corners of cases): available at any hardware store.
That's generally all I find myself needing for installing components, and you should be able to get all of them at even the smallest hardware store. Other useful tools include different sizes/lengths of screwdriver, and something to spread thermal paste with (such as an old credit card, or a razor blade) if you're installing a CPU. A few spare anti-static bags (you can get them at most computer stores, plus any hardware you buy comes in them) are useful, both as non-conductive surfaces for testing motherboards, and to put components in while they're not in a acse. You'll want a dremel (rotary tool) if you want to do any sort of case modding.
If you want to go fancier, you could try
this...