I did summer research in the ED, wrote an abstract, wrote an article, and took it to a regional conference in the fall and will be presenting it at a national conference in the Spring (well, I hope I get to present it...I'm not sure if the conference is during finals week). I chose to do research b/c I needed something that would boost my CV a bit, I needed to pay rent over the summer, and I was actually interested in it. I also got to spend time just hanging out in the ED and seeing patients, which I really enjoyed. The nature of my research was such that I was working from home most of the time and doing a lot of writing, so it was pretty much done on my schedule and I had plenty of time to hang out with friends, exercise, watch TV, and what not. My boyfriend even lived with me for a week and 2 of my college friends came down and visited me another week. It was definetly worth it.
Bottom line: do something you'll enjoy. This is the last big summer you'll have for awhile so don't commit yourself to research/teaching unless it's something that you'll really enjoy doing.