For some people, being taken out of their comfort zone in a fight can really panic them. Getting into close quarters is that particular place where taller fighters do not prefer to be. I would know, I'm a taller guy (77.5" reach, sup) who much prefers to use that reach to my advantage. That being said, once you get in, you could attack the body, but unless you're really adept at attacking the body, I'd say stick to head hunting with tight hooks and maybe uppercuts or overhands. Only because I think a lot of people drop their hands inadvertantly when going to the body, so headhunting can be a bigger payoff if you're not good workin' the body, is all.
Head movement is your friend when you're trying to get in the cut. If you want to be a little nasty you can cover up and try to let his punches meet your elbows on the way in. Using angles, like Adam said, is always smart and useful. Using feints is good too - fake a jab to get him to commit, and when he throws his counter jab slip it and step on in. Just remember that once you get in there to keep on him and don't let him get his reach back. The more times you have to try to get in, the more opportunities he'll have to start to figure your game and timing, and you don't want that.