Well the most popular is the one from proxylistscript.com since his source wasnt encoded many, many, many sites are running the leaked copy (warez) it was a $199 script. Wasnt worth that amount in my eyes after having bought it and was disappointed by its lack of features, much needed features.
Now for your project I would suggest chatting with Will as he has several licenses of this script and might allow you to use one for development of new templates.
Next popular one is the one that Will let out the bag and is spreading around to several proxy lists. So might be able to get him to give a copy of that for creating new designs.
Aside from those 2 the rest a fairly much garbage and wont live long. One was released in the DP proxy thread that has a few sites running it and in my eyes needs a template badly as it looks terrible with the stock design.