It's interesting that we are reviewing Google maps this week because just tonight I had a new client walk in saying she found Shanti Kitti Yoga using Google maps. That was the first time someone mentioned that. I don't use Google+ much, however, I can see where it would be useful in linking to other yoga communities and circles. I also learned about 'Hangout" which I would like to try for employee meetings.
I am not a fan of Yelp but I can see where it would be beneficial to have great reviews on there. I have had a couple great legitimate reviews from customers that they decided were not acceptable based on their standards so they refuse to add them. I also don't appreciate the fact that you have to pay them to remove your competitor's ads away from your site, since they put them there to begin with.
I have tried Groupon as well as Living Social and it has brought us a couple good clients, however, the majority were just looking for a discount and did not purchase anything after their coupon expired. I think those sites are useful for the exposure but in the yoga world, the student really needs to see the value of the classes and buying them at such a low price doesn't help them make that transition to actually paying for regularly priced classes.
Linked In is a great tool for connecting with other yoga teachers and studios. You can use it to find teachers as well ask for advice from other studio owners.