The big question is do you license strictly for stock, or do you also license for assignment? FotoQuote (which is what I use) is 'the industry standard' (self proclaimed though that may be), and truth-be-told that 'fact' does on occasion enter into my negotiation process if I get a balky client:

"Well, I don't know Mr. Hip Brand Manager, as you know we use FotoQuote because they are the industry standard for pricing and it tells me that we should be charging a minimum of $4,000 for that image usage despite your desire to obtain an unencumbered perpetual worldwide usage license for all mediums for $1.42 and a stick of gum that you found in your couch this afternoon. I could maybe take 10% off that price because you're a valued client, but I don't think I could go any lower than that."

It's sorta like the Kelly Blue Book... Sure there are other car pricing guides, but there's a certain amount of 'weight' that comes with it being a 'Blue Book Value.' They also cover both stock and assignment, licensing, and buyout... So you'll have all your bases covered in a single resource.

Having said all that, if you only do stock, I have a photographer friend who swears by HindSight's Photo Price Guide (unfortunately named, IMO). I have not used it, so I'm probably a poor salesman on the software, but as I understand it, it is cheaper than FotoQuote, they claim to have 'better' pricing models (whatever that means), allow you to add your own prices to their system, and they do offer a free trial so you can give it a test drive to see if it's to your liking (so does FotoQuote, btw).

In the free department (and I suspect that the old adage of 'you get what you pay for' applies here), and again if you're only looking for stock pricing guide, you might try out the Stock Photo Price Calculator. I have not personally used it, so consider it a pointer to a possible resource (if you're desperate and broke, I guess...), not a ringing endorsement. :-)

If you'd prefer a 'less automated' option, the organization American Photographic Artists (APA) has a business reference manual which provides a lot of really solid information and guidance on how to 'self-calculate' licensing and buyout fees across a variety of situations that you may encounter. The dues are relatively steep, so that may be something to take into consideration vs. simply springing for something like FotoQuote or HindSight.