As IT professionals, how do you evaluate your skill levels and thus how much you should be paid?

I'm on the outlook for another job. It's not that I don't like my current employer, but I strongly think that I'm being under paid... way under paid in comparison to my skills and job responsibilities. Let me first describe my job and my pay range, and you let me know if I should look for another job. Basically, I'm a do-it-all IT guy in a mid-size, multi-state, multi-location manufacturing company. I manage (9) Win2003 servers and the company's intranet. I also provide technical support to over 200 local and remote corporate users. On top of that, I have to develop software for company's internal use as needed. I also build and maintain about a dozen of company websites. And my current pay is under $50K/year.

So, my question is, should I stay with this job or should I start looking for another one? What's the pay range should I look for in New England area?
All inputs are greatly appreciated.