Government Wash for a couple nights on my way back from Zion in November. While I was there, I spotted a Campendium flag flying from a cluster of Airstreams on the hill. A little research led to a page for Campendium that noted it was still in beta but would be accepting new members shortly.
Leigh and Brian have lived and traveled full-time in Airstream trailers for several years, blogging about their experiences and their campsites on their Aluminarium blog. For the past couple years they have been developing Campendium to fill a need for a robust database of camping locations that spans the spectrum from free boondocking locations to high end RV parks.
In the past, I've used a variety of resources to locate potential camping locations but each source I tried had strengths and glaring weaknesses, requiring the use of many different resources to research an area of interest.
Campendium looks much better than any of the other online resources but is open by invitation only. I'd highly recommend to my traveling friends that you request an invitation - no charge. BTW, they also have a Facebook page where teaser campsite pictures are posted on a regular basis.
If you use Campendium, please give back by posting site reviews and/or linking appropriate blog posts. I'm impressed and I'm looking forward to using this tool when we wander the back roads of Utah and Colorado this summer.