http://groups.yahoo.com/group/j4x-owners-group/  a newsgroup for all J/4x's to share their experiences with boat maintenance, voyages or whatever you wish.  You can browse the discussions but to contribute you need to join the group by clicking the "Join This Group" link on the discussion group page. 
 

J/Boats - Design and marketing
 

Pearson Marine Group - former builder of J/Boats, previously known as TPI Composites; has some parts or can point you to suppliers
 

Songline's Cruising Classes and Island Charters - After cruising the J/42 for six years, Marc and Monica are now offering charters on their J42 Songline in and around the fantastic Santa Barbara Channel Islands, Southern California, USA