Some of our favourite links:

Uilleann Piping Sites:
Na Píobarí Uilleann
Uilleann Obsession

Pipers Gatherings (Tionóil):
CCÉ - Chris Langan - Toronto
The Pipers' Gathering - Killington, Vermont
The Northeast Tionól - East Durham NY
The St. Louis Tionól - St. Louis MO

Piping Forums on the Web:
Chiff & Fipple - Uilleann Pipe Forum
The Uilleann Forum

Other Clubs:
Irish Pipers Club - Québec
Irish Pipers Club - Seattle
Great Northern Irish Pipers Club - Minnesota
Salt Lake Piping Club
Long Island Uilleann Pipers Club
San Francisco Pipers Club

Some Tune sites on the web:
The Session
Ceolas - Fiddler's Companion
The Black Book
Alan Ng's Tunography
ABC Convert-o-matic