There’s a number of little tools emerging that pop up information from off-site when users hover over a link, but here’s the coolest one I’ve seen yet: Pop-up Politicians. This ajax widget from the Sunlight Foundation lets anyone link US Congressmembers’ names on their blogs to a popup window about that politician. Here’s an example of the tool in action. Bloggers covering matters of US politics can easily layer Sunlight’s widget into their posts – to add value to blog coverage and help a cool organization spread its work.

The window includes links to the politician’s page on Congresspedia, a wiki covering US Congress members, the page at OpenSecrets.org that tracks said politician’s campaign contributions and the Washington Post’s congressional voting database.

Chalk this one up as a simple, but truly useful, way that ajax, wikis and other Web 2.0 technologies are being leveraged.