Every franchised player costs their team cash equal to that player's franchise value, payable at the time the player is franchised. [FLOF Rules III.D.] This form gives owners a means to estimate a player's franchise value (FV) proir to the official declerations at the end of the NFL post-season.

Important Notes.
Since the advent of bonus points for yardage, the formulas used here typically underestimate the value of QBs and RBs who are any good. While I've never updated this for return yardage, experience shows that this will have minimal affect on FV, but for a couple players a year it might make a little bit of difference.

Stat Sources:

Obviously the more complete the information entered the better the estimate will be. That said, 2-pt conversions (which are seriously time consuming to collect) and random oddities (like DB's gaining receiving yards on 1 play a season) can generally be ignored without skewing the result much. Lost fumbles can be a factor if there are enough (look at QBs and RBs most). 2-pt conversions are only likely to affect QB values and then only rarely.

The best source for stats right now actually seems to be Yahoo.