I put together a two-drawer storage unit to go under my Engel fridge,
behind the front passenger's seat:

http://mira.sbw.org/photos/20091030/SN852141/

The top of the fridge is now just a little taller than the kitchen
unit.  The fridge lid just clears the curtain track:

http://mira.sbw.org/photos/20091030/SN852159/

The storage unit is secured to the seat belt attach points using the
kit GoWesty makes to secure the fridge:

http://mira.sbw.org/photos/20091030/SN852154/

The fridge is secured to the shelving unit using tie-down straps:

http://mira.sbw.org/photos/20091030/SN852147/

The whole thing is completely stable.

I used a post shelving system from Storables:

http://www.storables.com/Shop/Shelving/Steel-Shelving/

Alas, the sliding basket drawers are no longer available.  I had a
devil of a time getting these two.  Supposedly, they're introducing a
new product to replace them soon.

If I had any wordworking skillz, I could have built something more
attractive and not as heavy, but this'll do.