Ideas to make the car less stressful?

[Kiley Dozier-Bosanko]

I am very lucky that Mio (who is often sick) loves the car, however many of 
the furbabes  including my other kitty Oscar hate it.  They get incredibly 
stressed out and come home form the vet feeling worse then ever.  Does 
anyone have any tricks that have helped their cats stay calm?  I have heard 
of Feliway and catnip helping, but what else has helped?  Are there certain 
kinds of music that help?  What about allowing them to explore the car prior 
to longer trips?  Is the front seat better than the back?  I would 
appreciate hearing your suggestions.
Thank you,
Kiley