Listings for both paid and unpaid positions. A recent look showed about 100 berths available along many of the world's cruising routes, with about twice that many crew looking for berths.
Why you might want to act as crew on a cruising boat, both the obvious reasons and some less obvious.
Two unmoderated forums on finding crew / finding crewing berths. Useful, but caveat emptor when it comes to joining strangers on a cruising boat.
Here are Crew Available and Crew Wanted lists which a cruising sailor can search by type of sailing, geography, rig type, and other criteria.
On-line forum regarding cruising areas. Includes local facts and descriptions, charter information, crew available and wanted, Questions and answers format. No search.