This is a document that shows salary ranges for lots of IT positions and has geographical adjustment as well : http://s3.amazonaws.com/DBM/M3/2011/Downloads/RHT_2015_salar...

(anyone with other documentation that could easily be referenced in a salary negotiation?)

Another thing: I have an easy copy-paste response to recruiter cold contacts on linkedin where I say basically: I'm committed to my current company, but I'm always interested in real salary information, if you have something you can share I'd be happy to keep you in mind in the future. ... sometimes that gets me a number.

Having accurate information that you trust is half the battle IMO.