- Facebook seems to be the most popular,
- Twitter is the 'best' for shorter posts and for subscribing to news feeds,
- I honestly don't know where MySpace stands right now because it seems to have disappeared from the mainstream list of social networks,
- there's also Google+ whose best feature is the use of 'Circles' (their friend management system),
- Last.fm for music recommendations and making friends based on your taste in music
- and LinkedIn for making professional connections and promoting your business or resumé.

Due to the size, I vote for Facebook too.

Whatever social networking site will you choose, remember that if you want to effect SEO, you need to promote your content. But the most important for social networks is engaging with the audience, not just pushing your content. So keep it in mind.

Facebook, twitter, Google+ is the best social networking site for SEO.

I love to work on fb, twitter and g+.

I think Facebook, Twitter and also Google + are good social networking sites. But you can't ignore also Pinterest and Linkedin.

Linked in, Pinterest, You Tube, Facebook, Twitter, Stumble Upon, Myspace are all important social media sites that will help drive traffic to your website.

Now days Facebook, Twitter and Google plus are most popular in the market but I prefer most Google plus because I love that "Hangout" facility which is really best and helpful to me.

Dumb question...

For me its FACEBOOK.

Facebook
twitter
Google plus

Facebook, LinkedIn, google+ best social networking site.

Facebook.com is best social networking site.

The Google plus is the greatest social media networking site which other may aid! Google plus also approves the site with the profile and also update for getting the position.

Google plus can be considered to be the best choice that can assist you. It is true that Google Plus gives approval to your website that features your profile as well.