If you are a novice, beginner or intermediate bridge player looking to play bridge on-line, then almost certainly the best place is the Beginner/Intermediate Lounge (aka BIL) on Bridge Base Online.
Having just celebrated its third birthday, the BIL's founder, Maureen, runs the club to "provide the online bridge beginner and intermediate fraternity with a supportive, learning environment for developing and improving their bridge skills. A place to come together to learn, compete, make friends and form partnerships."
I don't know how many BIL members there are, but Maureen has a team of 180 (!!) experienced players who provide free group teaching sessions and mentoring. I run my sessions on Monday evenings for a couple of hours. The BIL calendar shows just how much is provided.
All you need to do is download the BBO software, become a member and then apply to join the BIL. Only advanced and better players are refused!
And did I mention that this is all free?