Nice holiday hack! Are you planning to keep it up-to-date? I would like to visit it every now and then to track updates along side other sites I have been checking for SOPA related stuff
So, other than the official co-sponsors, to determine someone's position, I just extrapolated from any historical information. For example, anyone who was on the judiciary committee who approved of PROTECT-IP's precursor (COICA in 2010) is likely, as far as we can know, a supporter of PROTECT-IP too.
I don't think such judgments of position can be made on campaign donations alone though. So it's an interesting challenge to think of ways to discern how engaged a Congressmember is on an issue based on the less publicized interactions he/she may have. Hopefully there's an easy way to collect such information that doesn't involve being a full-time researcher...but I plan to collect what I can and update for the time being.