BlogAds started as an online ad network for political blogs but now handle advertising for all categories. Perez Hilton, one of the biggest gossip and entertainment blogs, handles advertising through Blog Ads.
If there aren’t any paying sponsors, you may run your own in-house campaigns through the same ad units. You also have the option to offer discount codes to regular advertisers.
Unlike most ad networks that are CPC (click) or CPM based, BlogAds sell ads at a fixed price. Requires an invitation but you may ask any existing BlogAds publisher for one.