Extensive listings of upcoming events will be found in the canal-related magazines. Also check the Canal-Related Organisations page; follow the links there for the organisations that you're interested in to find possible event information.
Boat Jumbles page, from the Boat Jumble Association
London Canal Museum events
IWA Events and Festivals
Mikron Theatre Company
Folk on the Water - Link not working
Life and Times - folk duo; repertoire includes show entitled "Where the Working Boats Went"