Are you looking for just guilds which do the trials or a more hardcore progression guild?
Unholy Legacy are a good guild with relaxed fun members who do weekly trials.
You can always PM the guild leader @Flaminir if you're interested and have a chat with him about if it's something you might enjoy.
@Turelus - EU PC Megaserver "Don't count on others for help. In the end each of us is in this alone. The survivors are those who know how to look out for themselves."