Most IM residents work anywhere from 60-80 hrs per week, with at least one day off per week, and call schedules every 3rd or fourth night. This differs from rotation to rotation, program to program. When you are on call, most programs have a night float system that allows residents to go home and sleep these days too. It's really not as bad as it used to be, you can and many residents do have very active family lives outside of residency. I think that the hours are becoming comparable to a rigorous executive job in the business arena.
Moonlighting has gotten a little bit more difficult with the 80 hr work week (80 hr total is supposed to include all of your work hours, although technically, your program can only be responsible for hours you log into their hospital system. I don't know who would be looking for extra hours after the 80 hr work week to make a few extra dollars, but a chief resident told me that it's still a problem). A lot of programs offer moonlighting hours for residents during their elective months, when they are further away from the 80 hr limit. Also, there are still a lot of ER's/urgent care centers that are looking for IM and other residents who have completed their internship year and have passed step III to fill the overnight shifts. Anyways, it is still possible to moonlight at many programs during certain months, although I have also heard that some programs forbid it.
Work hours have limited call schedules and the 24+6 rule makes call a lot more manageable.
At least in my program, the interns have a quite nice lifestyle. It seems that things are turning to a team-based approach, meaning every team-member knows all the patients and can see them and present on rounds. You get 1 day off / week. We have 15 workdays / year of paid vacation. While internship is though as it is, it is getting easier in all fields due to the workhours restrictions. Moonlighting allowed from 2nd year on.