I seem to be able to get everything done with this:
http://www.harborfreight.com/16-piece-precision-screwdriver-set-4143.html
I only use one or two pieces from the set for frame and motor screws, but I use the other ones for other stuff. I also have a lot of random bit sets that I will sometimes use with electric drivers:
http://www.harborfreight.com/100-pc-security-bit-set-with-case-68457.html
I use that set the most for little stuff since it has everything, even odd security bits that most other sets don't have.
I'm a huge fan of Harbor Freight. Everything is cheap and they have an amazing selection of tools. Most of their stuff is good enough quality, but even if it's not, most of their hand tools have lifetime warranties and it's like the old school Sears warranties. If something breaks, you walk in there and tell them and they go grab one of the shelf, hand it to you, and send you on your way (at least in my experience).
Obviously, for certain things, I will splurge on a good name brand, but for these types of bits and drivers and whatnot, HF is the way to go if you have one near by. Just plug your nose when you go in there because it has an extremely strong odor of plastic and glue.