Guide to free social networks where you can meet and interact with people

We try to list here the most important social networks where people can discuss on various subjects and eventually meet each other or just exchange some information.

Must be split by category if possible. For example, a category for dating sites, one for sites with curiosities and other for sites related to professional meetings for people looking to find a job.

= English =

find people

 * bebo
 * pictari
 * orkut
 * friendster
 * stumbleupon

curiosities

 * guesswhatiheard

professional meetings

 * linkedin

other

 * 43things

= French =

find people

 * neurofriends

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May also be

 * webdate - not social?