It's funny to hear you guys go on about NC. I've lived here most of my life so it doesn't feel all that wonderful, but as far as cities go, Carrboro is one of my favorite. I have never had a bad time in Carrboro and I got my cat at one of the free markets you speak of.
I went to school in Greensboro for awhile in 2006 and 2007, but most of the venues that I used to go to (4 corners, Elam House, etc) have closed. I know only of The Hive and Somewhere Else Tavern now, that I'm sure are still open. The Hive is a collective-type place that has a free university and is a good place to stop in if you're traveling (free computer use, etc.) and SWET has had a couple shows that I enjoyed but usually I only frequent it for the people that go.
On Tate St. by UNC-G (and just a short walk from the RR tracks) there are a few bums that hang out and they'll help you find food if you are really desperate. There's a church that gets food deliveries every morning (usually bread, etc) and you're welcome to it. And there's a place called Jimmy-Johns that sells day-old bread for .50 (or gives it away free if you catch them right after they cash out the registers!) It's pretty easy to bum just about anything in Greensboro and there are plenty of train-hoppers to be found if you look in the right places. As far as sleeping on the streets goes, there's a set of abandoned tracks (surrounded by ones that are still used) once you get to the city part (a short hike from uncg) and there is a little hobotown you can pretty easily set up in. Dirty Rig and I slept under an overpass one night.
As far as UNC-Greensboro goes, DEFINITELY take advantage of everything you can while you're in Greensboro. Last Summer I was stuck in Greensboro for a week or so and Dirty Rig and I slept in the Meditation Room in the EUC building one morning after a particularly wet night. Just find a secluded spot in there and lay down. If you're around college-aged no one will say anything to you. If you can, socialize with some freshmen near the Cone and Reynolds buildings and you might be able to score your way into the building and sleep in the basement if you're good. They have nice couches and a kitchen and bathroom. As long as you make it look like you just 'forgot' to go back to your dorm you can pull it off. Leave the TV on or whatever. And you can probably find some nice students to buy you food since the freshman usually have unlimited meal plans. But beware, if you plan on pan-handling, you'll want to get a permit (free in Greensboro, $20 bucks in Raleigh and you'll need to provide information like address, SSN etc.)
RALEIGH: there are plenty plenty plenty of places to go here. For starters there's the GSS House (2) off of Western Blvd, Sadlack's off of Hillsborough St. (across from the belltower on NC State's campus) and the Brewery (as seen on American Hardcore, but I wouldn't recommend it anymore), and the ACRe collective on Mayview (?) which holds shows every now and then. When Dirty Rig and I were in Raleigh we spent a few days wandering the streets and when we got kicked out of Pullen Park (stupid rangers) we slept behind a building a few yards from the tracks. On the other side of the tracks was some type of prison which we didnt realize until after we'd settled down for the night. The homeless people/bums in Raleigh are very nice and will usually help you find free stuff (cigarettes, food, water, etc.). And if you have a little money, I'd suggest the NYPizza on Hillsborough St. Two slices and a drink for like 4 bucks and you can usually score some good crust if you keep an eye out.
And let's not forget dumpstering. There's a bruggers bagel place on Hillsborough st that you can go to right before they close and ask (not the manager!) one of the employees if they'll put the toss-outs right outside the back door instead of in the dumpster (or if you miss them, you can just get them out of the dumpster yourself, but they might be jeopardized.)
If anyone else is going to be in the raleigh area anytime soon, hit me up (PM me) and I'll see if I can't help you out a little!