This suggestion could get pretty complicated ... not sure where to stop and start with it ... but in general terms, it would be nice to have a place where people can go to 1. See what other people in the guild need to do, or what the guild needs to do ... IE Run Instance X or Farm resource Y ...
The big ???s are how much of it do you code, and how much of it do you leave open to people typing in random garbage that you might not want the guild to focus on ...
At it's simplest, you would just go there, because you need to run Shadow Lab for your Kara key, and type in : Need Shadow Lab Group. At it's most complicated you would select Instance, then Shadow Lab, then Kara Key .. and then be able to add a little note specific to what you need.
The more complicated approach would be good as it would allow you to group requests people make together ... and cross reference priests who need their D3 shoulders, and people who need a kara key ... but it then becomes a question of how do you handle more random ... less specific requests ...
Anyway, would prolly be good to get a dialog going about it on the forums here if you are at all interested in implementing something like this.
Set up the kara key as a key/attunement. Then your guildies will be able to check it off if they have it.
You can also make threads to help organize ppl who need to get certain things done. I.E. Make a Karazan thread and start adding posts telling guild members who do not have a key for kara to get their asses in gear.
you can peek at the roster (filtered by mains) to see who does and does not yet have a kara key.