Jack Norris is a registered dietitian (RD) and cofounder of Vegan Outreach :
Vegan Outreach -- Ending Cruelty to Animals
He maintains a sub0site called "Vegan Health"
Vegan Health.org : Home
He has written several articles on b-12. All cover the same ground, but some are shorter for people who aren't interested in details and others are longer for people who really want to get educated. Even the longer versions are not that long and are probably the best information on b-12 you will get anywhere:
Articles : Vitamin B12