Tumblr is a tricky one because of the community of members in it - Tumblr people can be pretty protective of their little space (remember when Yahoo first mentioned buying Tumblr over?). So infiltrating the Tumblr space with any kind of underlying commercial motive can backfire on you if you're not too careful. Do it right, and you'll have a good rep with tons of reblogs and such!
Instagram is a new social network however I am not sure if it can be used to utilize traffic and such because it is only for photos. Nothing works better than Facebook IMO. In choosing the right social networks we must know where are target market usually hangs out. We don't really need each and every working social network out there. Good luck!
You can try some bookmarking sites: prmsp.net bizsugar.com seobookmarking63.com newsseed.com stumbleupon.com prbookmarks.com quickieclick.com dzone.com dekut.com
No doubt that facebook good social networking site .. But TeenMing an education social networking sites and its mission is to provide a platform where schools, teachers and parents can communicate which will open new possibilities for students to learn, share and connect.
The best social network service ever made on this planet is vk.com. 1. Most powerful (you never do in fb you easily do in vk: targeting people, finding content) 2. Perfect usability (all in one or two clicks access; no one leading you in circles constantly trying to make money of you as FB does) 3. Million tons of free pirate content (everything they ever stole of music and video; 3rd biggest audio hosting of the planet, 4-th biggest video hosting). 4. Biggest social net in Europe BTW. Main problem:all around speaking in russian. But if you just see movies, listen music and looking for girlfriend it is not a problem at all.) PS A lot of ideas was stolen by Google+ and FB from this very project.
Facebook on top in social networking world, but myspace, twitter, linkdin also popular all over the world.
It depends on what you're into. There are social shopping networks to connect with friends, to share facts and news, to post cool things you love, to shop, and the list goes on. Since I am such an avid shopper, I really like to make use of the the social shopping networks (not to mention I work with them). I love the idea of social shopping in that you can ask for advice for your friends and trendsetters, find the best price, and even ask the brand itself about it's products. Usually when I go to buy something online I have about 12 different windows open, and this way you can do it all in one visit! Some of the best social shopping sites in my opinion are: Luvocrazy (more like pure style Pinterest), Fab (for some really original/trendy merchandise) Moodyo (a more personalized shopping experience) and Fancy (for more elitist crowd focused on style). You will be able to interact and share advice with other users on all of these platforms.
Na, I wouldn't consider Google+ a good social network. I like linkedin and concerning shopping and stuff Fab.