Wow. Go away on vacation and look what happens...
A group of about 40 people spent a weekend and ported Keith Brown's book The .NET Developer's Guide to Windows Security to a FlexWiki site here. Very sweet.
Part of the pluralsight.com FlexWiki site that's got material from Don Box, Craig Andera and Keith Brown.
I love discovering people who are using FlexWiki that I don't know about. It's clearly outgrown my ability to keep track of all the juicy things people are doing. If you know about cool places that FlexWiki is being used, please do try to add them to the IUseIt topic on flexwiki.com.