blo.gs is a service based on RSS feed aggregation, primarily from blogs, which produces a simple list (and also an RSS feed thereof) of the user's bookmarked sites, ordered according to recentness of update. It was acquired by Yahoo! in June 2005. On April 2009 the service had been transferred from Yahoo to Automattic, the business that runs WordPress.com.
The unconventional domain name is known as a domain hack.