The location of Justice Sunday III was recently announced in an email targeted at pastors in the Philadelphia area:

Greater Exodus Baptist Church in Philadelphia, Pennsylvania. :3

(per the article)

Greater Exodus seems to be affiliated with People for People (a group founded by a former NFL football player who became a pastor and who also was a member of the Fellowship of Christian Athletes--a group occasionally associated with "stealth evangelism" including "stealth altar calls" at public schools), and IS a Baptist church (per this this document) and apparently has quite a history of political involvement including crossing the line to frank politisation at times:

http://www.philadelphiaweekly.com/view.php?id=9034
http://www.pewtrusts.com/news/news_subpage.cfm?content_item_id=301&content_type_id=13&page=nr2 (includes actually hosting Republican National Convention events at the church itself--a definite legal no-no)
http://www.priestsforlife.org/news/01-07-04bushjuly4.htm
http://www.villagevoice.com/news/0031,dubya4,16951,6.html
http://www.pamspaulding.com/weblog/2005/01/can-gop-count-on-black-religious-vote.html

One of People For People's pet projects is voucher programs--not surprising as they run a charter school (registered as a 501(c)3) and the organisation itself is also registered as a 501(c)3.

Needless to say, the good folk at DefCon America and Talk2Action are being notified posthaste :3