The line-in jack really does need line-level to work properly. Some microphones might have enough, with the input gain all the way up, but it's not the best solution. Also, many require power, which isn't available.
There are USB mics and headsets available. I'm not familar with any particular make/model, though.
If you want to use a pro microphone, you'll need some sort of interface adapter. At that point, it's probably better to get a compete digital solution like the M-Audio Fast Track Pro. It has XLR inputs (with phantom power), analog and digital (optical) inputs/outputs, and is USB powered (even for phantom power).