Oh, say somewhere in the ball park of $50-75. Lightweight isn't a necessity, though it's preferred. I'm looking more for something rated well, but affordable.
In that price range (or thereabouts), I'd give consideration to buying used. Used tripods are a little safer than used cameras; there's nowhere near the delicacy of a camera or lens, and the operation is pretty easy to check -- if the parts that are supposed to move move they way they should, you're in pretty good shape.
I wrote some reviews for "budget" tripods that I've used over the years, and you might find some helpful info in there in terms of features, design considerations, etc. Of the three I reviewed, something like the Induro might be the best bet for you -- it's right on the low end of what I think I'd want to trust with a 5D. If you want to read the others to get an idea of some of the features that are available, etc., it might help you understand what you're shopping for a little better.
LambertPix » Budget tripod shootout, part 1 (Velbon CX-300)
LambertPix » Budget tripod shootout, part 2 (Dolica AX620B100)
LambertPix » Budget tripod shootout, Part 3 (Induro A113 / SA01)
There are some features that depend pretty highly on personal preference - twist locks vs. flip locks, for example. You probably need to figure out whether you've got a preference for one vs. the other. When you get to the head, try to understand if you want / need features beyond a basic ballhead, because there are a lot of nice options out there if you spend the money. Give some thought to the quick-release system, too -- this might be the time to move to a semi-standardized design like Arca.
FWIW, I'm using a Manfrotto 190CXPro4 with a Giottos ballhead now, and I'm generally very happy with it, but it's a bit beyond your budgeted amount. I use my tripod pretty extensively, though, so the extra investment made sense for me.