I've got some good stores, but I unfortunately live completely on the other side of Houston. So don't expect these places to be close. But they're OH so useful. For instance:
Metal Supermarkets 24 min away, but likely to have a large selection of raw stock you might need for that repair. Call (713)934-3838 to see. Hours 7:30am-5:00pm. We'll have a catalog in the pit.
Turner Hardware 21 min away. A great hardware store. Huge selection of nuts, bolts, and screws, even metric. Some aluminum and steel angle as well. Open Saturdays.
Bass Tool 19 min away. Just about every tool you could ever want. Need a .1248 chucking reamer? It's in stock and will be waiting in Will Call. Great if the machine shop says they need a certain tool to help you out. Check the catalog at
http://www.basstool.com/ Open till Noon on Saturdays. We'll have the Bass catalog too.
Ace Electronics 20 min away. A rather large selection of electronic bits and pieces and tools. Not open saturdays, though. Just 8a-5p weekdays. Knowledgable staff, though.
Electronic Parts Outlet 15 or so min away. The Westpark Tollway is EZ-Tag only, so you'll probably want to avoid it. Bring me a map at 57's pit and I'll get you there. More electronics goodness. Huge selection of all sorts of stuff, but a bit hit or miss. Careful you don't get stuck staring at all the neat doodads. Open saturday mornings, but their website's down. I'll call tomorrow and find out what's up with that.
Fry's Electronics 21 min away. I usually leave my wallet at home or bring a chaperone. Otherwise I walk out with Guitar Hero or a new wireless mouse. Large electronics parts section, ICs and all. Also computer stuff and home appliances. In case your robot really needs a fridge to keep those motors ice cold.
And a few places a little closer...
RadioShack
Walmart
Grainger You know, Grainger. Lots of parts and shaft collars and bearings and all sorts of goodies. Open 7:30a - 5p, weekdays. Call 713-748-8280 to check for things in stock. We'll have a catalog in our pit.