Some links which are absolutely worth reading:
The rulebook - LRB6. This is roughly what BB2 is working to, although there are some changes. See "The NAF" link at the bottom for what it is thought those changes are. The NAF also provide lots of links to the rules including a number of clarifications.
BBTactics - not only a BB league in and of itself, but a great resource for articles such as cage breaking and how to beat Dwarves.
The Taouch! of Blood Bowl - great general strategy guide for newbies.
The Art of Blocking - assists, how they work, and how to set them up. PDF download.
Individual racial guides - includes roster tips and options.
One turn touchdowns - turn 16, you've just been scored against to make it 2-2 and your opponent thinks the draw is all you will manage? Time to think again...
Playbooks - a list of strategy guides for each race. Includes Bretonnians. NOTE: not all the teams or star players in these guides are available in BB2. Yet(?).
The NAF - The NAF is an organisation which is mainly tabletop oriented, but they obviously have an interest in online. The link includes a list of known discrepancies between online and CRP.
The 1000 Losses Playbook (PDF download) - the wisdom of a very experienced coach who not only has over 1000 losses to his name, but over 2500 wins.
cknoor's video guides - I'm told they are very good.
Probability - a brief guide on probabilities and dice.
Samba Action Calculator - an awesome little tool from Elyoukey which can string together potential moves to see what the odds are. So when your opponent did that dodge, hand off, pass, scatter, catch and 2 GFIs into the endzone to win you can work out exactly how lucky he was. Because that's important!