A free, community driven Q&A website.
Probably the best polish mathematical site. Interesting discussions and lots of helpful people make it the most pleasant community board of that kind.
Free social networking and micro-blogging service that allows its users to send and read other users' updates.
The world's largest social music platform. Show off your taste, see what your friends are listening to, hear new music, get personal radio, recommendations, and downloads, all for free.
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Scientific physics forums for professionals and students to discuss serious issues and topics regarding physics in theory, practice, study and reality.
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