Washingtonpost.com has a great new tool for tracking political advertising called Mixed Messages:

The database includes political advertisements funded by campaigns, parties, committees, and independent advocacy groups. Most of the ads are tied to specific U.S. House, U.S. Senate, or gubernatorial races throughout the country. Some of the ads are more general "issue" or advocacy ads not tied to a particular race or candidate. You can search for ads based on the criteria listed below.

The creator of this database, Adrian Holovaty, talks about it on his blog:

Mixed Messages is a database of political campaign ads from across the country. The washingtonpost.com political team has collected and categorized dozens of these ads according to a wide array of criteria, such as the ad's music (patriotic, somber, ominous, upbeat), issues mentioned (the economy, crime, etc.), ad characters (firemen, farmers, blue collar workers, teachers) and common visual cues and cliches (American flags, soldiers, black and white photography, images of Sept. 11). It's fun -- and revealing -- to explore the ads in these various ways.

We've also tagged each ad by year, state, candidate, political party, funding source, tone, narrator gender, language and dissemination (TV, Web, radio).