FUNDSVCS. Advancement and development services and related issues. One of the best forums for discussion of IRS and tax issues related to giving, policies and procedures, gifts and records processing, and data management. Wealth of knowledge through the many participants. Extensive listserv archives.
Related site also includes download area. Tends to be more higher education focused but a number of other verticals within the sector are often represented. Lots of items such as policies and procedures and other resources available for download in the downloads area.