Nielsen/NetRatings' August stats for social network use in the US show continued growth for Facebook and business network LinkedIn.
Facebook increased its number of unique users by 117% year-on-year to reach 19.1m, while business social network LinkedIn had 4.4m, up 163%.
The site with the highest growth rate, however, was Buzznet.com, a social network centred around music.
It has grown by an impressive 405% since last August, and had 3.8m unique users last month.
Also showing impressive growth was Club Penguin, the children's virtual world/social network, which was acquired by Disney recently in a deal worth $700m (£345m). It increased its number of US users by 250% to 3.9m.
Stats for online video sites confirm the dominance of YouTube, which grew its traffic by 66%, reaching 56.4m US users, though Veoh was the biggest gainer, increasing its number of users by 346% to 2.9m.
Internet Statistics Compendium - September 2007