Hi there i'm coach Titan and i play in the MBBL2 Play-by-Email (better than it sounds ) league. Pbem of course doesn't take up too much time so its in no way mutually exclusive with tabletop leagues or the computer game, its just a little something extra :D.
Despite the fact the our league is owned by Galak aka Tom Anders a major factor in creating the new LRB's, despite that gamesworkshop made him give up our old bloodbowl.net address which some might be familiar with. So we're now at http://www.midgardbb.com/MBBL2/ .
Our league now has 89 races!!!!!. We technically use the old LRB4 rules but with all the custom stuff that doesn't really matter. We have a handicap table very similar to the LRB6 cards and other custom rules including extra skills, secretweapons, coachs, personalapoths, onpitchspellcasters etc. You can also have up to 4 active teams at a time. Anyone interested in playing in the worlds most variety packed bloodbowl league check it out.
Extra help can be found in my personal bit of webspace http://www.titan.my-php.net . I recently added a quickreference zip which has all the rules and teamreference sheets handy.
To get started you signup in our forum then, post in the joining post which is in the MBBL2Questions section.