1996 Nissan Sentra Starting (starter?) Problem

Dome light got left on overnight last week. Starter turned slowly the next morning, but started engine so I thought battery was drained, but alternator would recharge. Then, I left town for three days for work, got back last night, jumped in my car and it started even more slowly. This morning, started even more slowly, like I thought it wouldn't, but then it did. Stopped to get gas (wasn't on empty) and then tried to start back up. Starter turned slowly three or four times, then stopped. Tried again, barely turned once, then stopped. Then wouldn't turn. Had someone try to jump start, no turn. Radio, power windows, headlights all worked, but no turn. Couple of the attendants helped to push to see if I could push start it. Popped the clutch three different times but it never fired up. Didn't have much room in the parking lot so I didn't try anymore. I just parked it and then took the battery out, and took to be tested. Cleaned the posts and the terminals. It tested fine, then had it charged. Hooked it back up. No turn. I need some quick (and cheap) diagnosis ideas before I have to have it towed to a mechanic. Any ideas?