The Wikio rankings are a measure of how much blogs are being “talked about” on other independent sites, and are produced by Wikio for a number of categories of blogs in Europe and North America, including politics, techology, culture and even Wine and Beer.
The Wikio ranking is measured by incoming editorial links (i.e., not blogrolls) from blogs registered with Wikio which appear in RSS feeds. To be clear (again), this is no measure of traffic. Links are weighted by time, prominence of the linking blog, and prominence of the link in the linking article.
There is also a toolkit, Wikio Labs, which allows you to dig down into the detail to the level of individual links.
This month I have advanced notice of the “Overall” rankings, which are below.
(Disclosure: I am the “Host” of the UK Wikio Politics rankings. The position is unpaid.)