Yes you can hook up a hose to your rain barrel. You want to go to the hardware store and get a special fitting to fit to a hole near the bottom of your barrel. You will then attach a garden spigot/valve to this bulwark fitting. The fitting is basically 2 flanges, one with a threaded male part, another with a threaded female part. Put 2 washers on it, one on the inside of the barrel with the inside flange, one on the outside with the outside fitting.

Drill a hole about 6" from the bottom so debris does not get stuck in the outlet when you open the spigot for your hose. Place the barrel on 2 levels of cinder blocks to make it about 10-12" above ground. Then collect water, attach hose, and you're all set.

I got 2 50 gal barrels from Freecycle for free. They are plastic. But I just haven't put the garden spigot on them yet.

I'm also collecting condensation from my air conditioner. A hose runs from inside my hose to the backyard, which is attached to a pump which pumps out AC condensation. So I just extended this hose to a 5 gal bucket. When the AC is running all day I get about 2 gallons per day of clear water.

The condensation comes from the actual cooling coils located right above your furnace in the main ductwork. When these coils are installed it almost always includes a way to drain away condensation, usually to a drain in your utility room since that's where modern furnaces are located now.

My central A/C unit drains in the basement. I could collect for houseplants I guess but it would be hard to use outside. It has been putting out about 3 gallons a day I'd guess though with all this heat recently.

Should an outdoor barrel be drained in winter so as to avoid cracking from freezing?

i dont know about the kit from the hardware store but heres what i did. I got a 55 gallon plastic drum. it should come with 2 screw in bungs. at least one of the bungs should have a 1/2" or 3/4" prethreaded hole in the center of it. (its not actually a hole but its a threaded counterbore with a knockout in the bottom of it) all you have to do is buy a brass hose spigot with the right threads to fit the counter bored hole. thread it into the hole until it bottoms out by hand the then keep going with a wrench. the bottom of the hole in the bung will pop out. now as you look at the barrel you have a spigot sticking out of the top of it. i turned my barrel upside down and placed it on 3 concrete blocks. this has the added effect of increasing the water pressure at the end of the hose since the barrel is a bit higher and the spigot is at the absolute bottom of the barrel. I cut the entire bottom (which is now the top) of the barrel out. this makes it easier to clean and scoop out any floating debris.

"Should an outdoor barrel be drained in winter so as to avoid cracking from freezing?"

... Yes, in most cases. I'm using some big "Rubbermaid" trash cans which will take the freeze but they are a lot wider at the top than at the bottom, giving the ice room to expand. You're safer draining your barrels.