Many websites have been launched to provide various members opportunities to post about topics which they like. Google likes niche websites i.e. those website which are specialized for a particular topic for by launching specific websites and working on them in a focussed way you will receive better earnings from Adsense.
It is up to you to decide in which topics your interests lay and accordingly decide which site to join.
These type of sites are mainly suits for the people who really wants to know about the specific field and to share their views regarding to it. So this site cannot be suitable for all the people who really not interested on knowing about the Google+.
Mr. Sankara Rama Subramanian