Most employers I know laugh at you if you flip a print out of salary.com in front of them.
Salaries are a funny thing though. Unless you are in a government job with very set pay guidelines, it's almost impossible to tell you what you *could* be making. It's really about how much your company values you, and how much brass you have to demand more when you are think you are worth it.
I've increased my salary nearly 50% in 4 years because I've gone in and told them that I was worth way more than what I was being paid. They sat on it for a bit, did some research, saw how much work I was doing and agreed to what I was asking.
If you think you are being underpaid, don't be afraid to ask for more. Unless they are total jackasses they aren't going to dump somebody that's put 4.5 years into a company and knows how the company works and waste their time retraining a new employee. Shot a bit higher than what you want, they'll take it or come back with a counter.
You never get a *real* raise until you ask...or at least threaten to leave
