The CFA is a great league which can be found at http://cfa-football.com/ . It has very active owners and a great commish, however there are two openings in the 32-team league, including the team that just won the championship. You can contact PM the commissioner on the site if you are interested.
I encourage you to join if you are looking for a challenge or just get your start in PFS leagues.
In case you don't know, PFS (Pro Football Simulator) is a football simulation game optimized for online play. It can be purchased for $25 at barcodegames.com/