Someone probably already thought of this idea, probably more than one person, but it seems cool to me anyway and it's easily accomplished, thanks to groups like Open Secrets.
What if, when a member of Congress is speaking on the floor of the Senate or House and it's being broadcast on C-SPAN, a list comes up that gives specific information about who gave that person the most money in campaign contributions? One of the great things about consumers of information in 2009 is thanks to social media tools they've become much more adept at processing multiple bits of information at once. It's not hard to listen to someone speak while perusing a list.
To prevent overkill, I think it's sufficient to include, say, the top ten contributors for the most recent election cycle, even though that doesn't really tell the whole story either. But I've noticed an emerging and frankly exciting trend as of late - people who consume news about politics are becoming much more savvy about how the process works and what really influences members of Congress.
I've included here a rather sloppy artist's rendition of what it might look like for the Senators from my state - forgive me, I'm not what you'd call an expert at photoshop. But when there's a debate on the floor of the Senate (or the House) and you hear a member advocate for a particular point of view or commercial interest, it's nice to know if that person has been taking contributions from a relevant party.
I wouldn't DREAM of accusing any particular member of Congress for being a paid spokesperson for any particular company or industry - mostly because so many of them insist that the thousands upon thousands of dollars they accept have absolutely no influence over their votes whatsoever. (uh-huh.) But I do think this is publicly available information that people deserve to have top-of-mind during any policy debate.
An alternative to this would be to amend the dress codes for the House and Senate floor. Rather than jackets and ties for gentleman and similar appropriate dress for ladies, I might suggest the suits NASCAR drivers wear with the logos of the companies who provide "sponsorships" plastered all over them.