LJ removed the ability to search for community info. If you are a paid member, you can use this:
community_quest. LJ user
spacefem also created a simple search box for this purpose. Note that it is powered by privacy vampire, Google:
(You can also, of course, search via the INTERESTS listed on user and community profile pages).
Note that I could not find the old, "Search by Interest," link on the NEW LJ design, so I went back and grabbed it - along with others, so here they are. SEARCH BY:
Interests Random Region(?)
School Directory Search The Community Center LiveJournal text search