Is there a way to find out what yahoo!group has the most posts, members, post per members, etc.?

20 members. 12 of who actually post. 92K posts in a little over 3 years. No one's close.

According to a 12/27/07 Moderator Central newsletter from Jami Heidt of Yahoo, as of November 1, 2007, the largest Yahoo! Group, FlyLadyMentors, exceeded 450,000 members. I just checked that group and there currently are 469,473 members and 51,301 messages in it's archives which would not include any posts that might have been deleted one way or another. To get the number of posts per member, you would have to go to that site and tally them yourself. The archives are public so you would not have to join the group to view posts.

only way is to scroll the directory and take a look however, that directory will not include closed groups so you'll never get an accurate answer.