For those new (or not so new) players who are looking for a guild to join, it's a bit tiresome to have to browse the forums searching one according to our needs. A guild directory would do the trick very well. Every guild could be listed by the following aspects:
-Language (English by default, when searching you can choose more than one language to include more guilds)
-Number of members (you can specify a rank)
-Level (or rank of levels)
-Activity time (which hours the guild members are usually active, the guild creator would be the one to determinate this at first, though a statistical auto-updating wouldn't be out of the question)
-Play style (maybe with keywords, fixed by the owner)
This last one is the one MORE IMPORTANT criterium for me (maybe with the activity time), and the reason I haven't joined a guild yet.