First it depends on your budget and how casual your shooting. You can get a good Rebel for about $700 with lens. This also allows you to get into the habit of shooting digitally in manual format and it isn't a weight to lug around. It will also free up some money for a lens or two (which is where the real investment is).
If breaching the grand mark isn't going to be an issue and you are getting pretty serious, then I would straight-up choose a 7D.
I myself use a 7D and think it is the most useful thing I could have. There are quite a bit of fun elements in there, but I'll just go over the stuff I have a lot of experience with or that is notable.
I'm mainly a sports, especially track&field, photographer, so the 8fps was the first thing I gravitated towards. What is also nice is how many frames you can cram in one setting (at least 70 in JPEG and ).
The second was the 19 AF points which allows greater flexibility.
18mp is nice, but wasn't a great concern when I chose this camera.
I haven't used it much, but when I have, the fact that a slave-master is built into the flash was extremely helpful.
I personally could really care less about the 1080p video setting; however, the tilt/elevation tool was helpful whenever I shot buildings.
Finer control of the ISO (as opposed to my previous 400D) was useful as was the amount of noise that was reduced.
The fact that it can go up to 1/8000 of a second can sound a bit ridiculous, but I got some use it of it when shooting some landscape shots on a sunny day.
Oh and since I go around to a lot of places, and the potential for elemental abuse is high, the fact that it is solidly built and weather-sealed is an extreme plus.
Even when factoring price, I'd pick the 7D over the 60D (a $400 jump really isn't bad all things considered). It has also got a bit of tenure as opposed to the 60D.
If money really isn't going to be an issue and you aren't going to be focusing on action, might as well get the 5DmkII. It definitely has positive tenure (never got to try it myself, so this is just by reputation) and, with a full frame, you will be getting more out of that heightened mp range.
Some other things you will need regardless of the camera you get (other than lenses of course).
Most importantly, buy a flash, and don't rely on the pop-up (that will be $300-500 for a good one).
The more memory cards, the better. One meet, I ended up shooting about 1,400 shots a day; even with a 8g UDMA card (and a friend's house next-door that I could easily run over and dump some excess shots during breaktime) those spare 2gigs were a lifesaver. Same goes for an extra battery.
Stabilizing device: tripod, monopod, one of those little table-top tripods.
A couple sample shots from my 7D.
An idea of how the framerate is.
This was when I was just learning how to work the slave-master.