I am living in a house where most electrical outlets are two prong. There are a smattering of three prong, in particular where an addition was put on. Am I hosed when it comes to where I can plug in electrical appliances that have three prong plugs?
I'm assuming you're in the US.
Get a tester and see if the box is grounded. A two lead neon type tester works well for this. Insert one lead into one side of the two-prong outlet and touch the other lead to the screw that holds the plate on. Try the other side, too. You may have to scratch off some paint if the screw isn't bare metal. If it lights up that's good news. You can use a multi-meter set to read AC voltage or another type of tester instead of the neon one.
If you have grounded boxes, you can either buy two-prong to three prong adapters that have a lug that you put the plate's screw through or you can buy replacement outlets that are designed for retrofitting in this application.
Your other option is to have an electrician come in and upgrade your wiring to full grounding.
Depends. It may be that the additional wire was just never terminated. You can see if you have all three pairs by shutting off the breaker, taking off the outlet cover and examining the wires going to your outlets. It may just be snipped off and you can put in the third leg rather easily.
You are most likely hosed. It's highly unlikely you'd find a usable ground wire if your receptacles are not grounded. Don't use the cheater adapters if the box isn't grounded- they're not safe. If an appliance has a ground prong, it's not double-insulated, meaning there are places on it you could touch and possibly be electrocuted if your body is a better path to ground than whatever else it's touching. It needs to be on a grounded circuit.
We skipped over several apartments and houses for lack of grounded outlets.
In certain areas it is required to have 3 prong grounded outlets to get a CO (certificate of occupancy). Meaning you technically can not move into your new or new to you house until this problem is fixed. While flipping houses i came across this a lot and in each case the CO inspector said i could install a GFI outlet in replace of an ungrounded outlet and pass. GFI's can get expensive so you can install one GFI on the first outlet of a series of outlets and it will protect every outlet connected after it. Meaning you can install regular 3 prong outlets. The gfi should come with stickers saying gfi protected. Put these on the regular outlets you install.
I'm sure there will be people who will give a 2 page technical explanation on why this doesn't protect you but don't listen. It works and is code officer approved.