From a more "inside" point of view (Sorry, Tabbs), most of the guilds on that list are pretty much history, while some others aren´t even on that list.
Guilds I´ve seen lately (In no special order):
Community of Skara-Brae (mainly frankophone) (S-B)
Flolen D´ Lloth (Drow; if anyone finds a typo, keep it!) (F^L)
Vesper Trading Company/Vesper Militia (VTC / -V- )
Guardsmen Militia (Yew) (Grd)
Barony of Cove (BoC)
Sterling&Kendall Trading Company (S-K)
Britannian Guards (LB)
Brigands of the Fort (B^F)
Duchy of Trinsic (DoT)
You are most likely to find someone between 8 and 12 pm BST.
Also check this:
Ye Sosarian Morning Poste - Page 9 - Forums4Games
and this:
CoRE Member Guild Forums - Forums4Games