Harbor Freight is a great place to get tools. They have many types of tools. Everything from construction supplies to home and garage essentials to automotive repair tools. They have a good supply of air tools and hand tools as well.
Some of the things that I buy there are some shop supplies (as long as they are cheaper than the auto parts stores), air tools that I don't use often. Things that are way more expensive anywhere else, but that I don't use very often. Tool trays and tables, etc.
My only caution is that many of the things that they sell are not of the greatest quality. For someone who doesn't use the tools that much quality is not a big deal, but if you are looking for something that you can use a lot and abuse it, then this tool store may not be for you.
Things that I would not buy there are things like air tools that I use all the time and need the best quality, hand tools that I use all the time like screwdrivers, wrenches, etc., welding equipment. With these types of tools and shop equipment you simply can't skimp. You need quality. While this store does carry things of quality you have to inspect each item carefully to be sure that it will do the job that you need it to.
If you buy a cheap wrench you'll likely end up with skinned knuckles, if you buy cheap screwdrivers you'll end up with stripped screws. It's simply not worth the trouble to buy these types of tools unless you are buying good quality tools.
Harbor Freight is a great resource for certain types of tools and automotive supplies, especially for the home mechanic. Some of their shop equipment probably wouldn't hold up to the rigors of an auto repair shop environment, but most of them would work just fine in a home garage.
If you are looking for simple tools and basic supplies (things like gloves, towels, etc), then I would get them here.
Update: Having bought countless items from different retail shops and websites over the years, I now buy almost all auto parts, tools and supplies from Amazon: Automotive.
I begun buying vehicle replacement parts on Amazon a few years ago due to the cost savings and convenience. I find that Amazon sells most automotive products about 20 to 30% cheaper than retail stores, plus the free shipping helps me cut down traveling expenses and time.
Amazon's Automotive Part Finder also makes it a breeze to find the correct parts and accessories. All I have to do is to enter the vehicle year, make and model... and Amazon will show me a list of parts which fit that specific vehicle.
If you sign up for Amazon Prime, you can expect to receive most items within two days. This is far quicker than other online auto retailers who often take 5 to 14 days to deliver.