It all depends on when you what to go. Right now it is pretty busy in the main campgrounds due to Spring Break and most of the parks still having the winter guests occupying alot of the space. There are a handfull of good places, here are ones I can remember.
* Crazyhorse (Space right on the water)
* Islander (on the water)
* Beachcomber (on the water)
* Sandpoint (on the water, south of town)
* Lake Havasu RV Park (North end of town)
* Havasu Falls RV (also on the North side)
All of these are nice parks with full hook ups. I spend most of the summer at Crazyhorse since they have boats slips and a VIP area.
Good luck and enjoy. It is a great time of the year in Havi right now.