The Yahoo EN500 Group
Lots of useful mod and how-to's. Vulcan Riders and Owners Club. Originally started by some Vulcan 1500 owners. Page of another Vulcan 500 owner unfortunately like this page lots of it "Coming Soon."
If you can read German.  

Dirty Girl's Vulcan Page  A racer who has put over 100K kilometeres on her Vulcan 500. and
Two pages dedicated to the Kawasaki 454 LTD The immediate predecessor to the vulcan 500 (EN500A) 
The Vulcan 750 is practically the same bike as the EN500A ('90-'96 Vulcan 500) except with a V-twin where our parallel twin engine should be.