After quite some time spent on this, I am proud to present my most recent project: CheckRoles.
CheckRoles allows somebody (most likely a raid leader) to request role and gear information from either the entire guild or the current raid group.
This will then display what specs each player can play and the gear he has available for those specs.
To be displayed here, each player first has to create sets of gear and assign them to his specs.
The addon is currently in open beta testing, so drop by WoWace or Curse and start using it if you're interested.
Any bug reports or suggestions either here or on the respective comment pages on WoWace/Curse are highly appreciated.
EDIT: Since people have been asking this a lot - both the requesting person and the requested person need to have the addon.