Hi WGT,
I'd like to recommend a 'groups' option within the friends list.
Something similar to what most instant messenger programs utilize (or Skype, for that matter). It would be really useful to have the ability to create groups, and drag different users into different groups, then be able to choose which groups are hidden or shown.
For instance, a current comp I am involved in - it would be great to drag users involved in the same comp into a group, and to be able to tell when those players are available for a game.