I stumbled on PayScale's salary negotiation guide today. It has a ton of helpful resources. My favorite is the PayScale Salary Report tool (just click on the first button 'Find out what you're worth'). Once you input your anonymous information like job title, job responsibilities, and location, it spits out the average salary for your area in addition to some other useful info such as possible career progression titles and cost of living expenses. This is a great tool for quickly gathering a basic salary number so you know if what you are getting paid for your area is comparable.
I highly recommend checking it out!