NAF World Headquarters - Online league and player resources such as a forum. - http://www.bloodbowl.net
Online Blood Bowl League - A league site with various resources relating to the 3rd edition of the game. Uses BBIrc client to play. - http://www.olbbl.com
FUMBBL - Fully automated league following the LRB ruleset using the JavaBowl client. - http://fumbbl.com
MBBL2 League - A PBeM Blood Bowl league with many rosters to choose from. - http://www.blood-bowl.net/MBBL2/MBBL2Rules.html
Really 'Ard Blood Bowl League - Contains information concerning an online PBeM league. - http://www.dn-allen.supanet.com/RABBL.html