I joined a guild with 260 characters, many of them alts and whatnot. Is there a guild panel out there that allows some filtering? It's quite annoying to find people in such a huge list

Judging by the lack of replies, no. It sure would be a handy thing though, to be able to filter by keys or being saved to a raid, or show alts as mains, separate raiders from members, etc.

I use GuildFu, a plugin for fubar. It's a pretty nice interface, and has some filtering options that I haven't personally toyed with, but it may be worth your while to look into.

Link: http://www.wowace.com/wiki/FuBar_GuildFu