MAPLight.org offers a well-designed interface for a rich dataset of bills, legislators, and money. Studying relationships between contributions and legislative voting is something of a tradition. Now everyone can join in!
Users can discover not only who gives the most, but the "success rates" for such "investments" (i.e., whether politicians supported their position). The data currently covers just California, but the plan is to add Congress next. Any chance this may improve the quality of political journalism? Of scholarship?
NOTE: Michael Calore has a write-up about MapLight on Wired.com: "Web Mashups Turn Citizens Into Washington's Newest Watchdogs."
UPDATE 5-17-07: MAPLight Congress is now live.