Organising Raids

So, our guilds version of organising raids is to have an Absent forum, in which players give a reason if they can not make a raid.....

Then in the game the post a time people are meant to arrive, at an unknown location, to fight an unknown boss....

This is due to the fact that the guild doesn't know what encounter we can complete successfully, based on what players we have online at the given raid time....

Which I fully understand, without a pali tank we can't do x, with a druid tank we can do x, with no mage we can't do x, it makes sence, but its not very efficent...

In an attempt to rectify the situation I have started making threads on the forums we have so that people can /sign saying they will attend the raid tonight....I was hoping this would allow the Officers to say, we can do Gruul, Mag, Lurker what ever tonight because we know we have x,x & x....

Its still not a very good way of keeping track of the players though, if one can't get to the internet before the game, we won't know till raid time any way....

So I ask you, what does your guild do to keep track of what the next enemy you will conquor be, and how do you keep track of who will be attending prior to the raid actually starting???