Feedster, the search engine and advertising network for blogs and RSS feeds, announced today that it has launched the Feedster Top 500, a new ranking of "the most interesting and important blogs in the U.S." (via MediaBuyerPlanner). The ranking is based on number of inbound links over time and whether the blog has been updated recently, among other factors. It also eliminates "obvious" non-blogs that have appeared on other top blog lists and moves away from ranking based on which blogs have been around the longest.

The ranking has also left out professional news sites, aggregation systems, and "some fairly static websites that happened to have feeds but don't feel bloggy," according to the creator of the Feedster Top 500, J. Scott Johnson, who is also a Feedster cofounder and its CTO.

This sort of filtering is different from what Feedster uses to categorize news versus blogs in Feedster search, and is much more subjective, Johnson adds. "As the blog world rapidly changes, we will quickly update our ranking methods to keep up."

The Feedster Top 500 will be updated each month.