Everyone is familiar with Twitter, Facebook and LinkedIn. But how many social media sites are there in the market? According to KnowledgeNetworks, here’s a list (in no particular order) of “commonly categorized” social media sites:

Bebo.com

Flixster.com

Myyearbook.com

Blackplanet.com

Friendster.com

Ning.com

Cafemom.com

Hi5.com

Picasa.com

Classmates.com

Imeem.com

Plaxo.com

ClubPenguin.com

Last.fm

Reddit.com

Del.icio.us

Live.com

Reunion.com

Digg.com

LinkedIn.com

Tagged.com

Facebook.com

Livejournal.com

Twitter.com

Flickr.com

Myspace.com

YouTube.com