For deep sky targets, aperture is king. The cheapest telescope likely to make you happy is an 8-inch Dobsonian, though larger is better. Dobs have no computerization and you have to push them to follow objects, but they give the brightest image for the money. How large a Dob you can fit in your car and still carry passengers is another question. Check out Orion at Telescope.com if you want a Dob.
The Meade ETX line is fun--I own two ETX90s, though I use one as a guide scope on the side of my "real" telescope (a 10-inch Meade LX200 GPS), and the other I use for schoolchild presentations. The aperture of even the largest ETX is too small for serious deep-sky work, though the portability is wonderful, and they give decent planetary views. They also can be used as daytime scopes for birding or whatever.
If you can spend in the $1000 range, consider the LXD-55 line from Meade, either the 8-inch Schmidt-Newtonian or the 8-inch Schmidt-Cassegrain.
If you have more like $1700 to $2000, consider the Meade LX-90 8-inch. It will do superb planetary work and can double as a deep-sky visual scope. For those who want a one-scope-does-it-all-for-planets-and-deep-sky scope, a Schmidt-Cassegrain from either Meade or Celestron is probably the best compromise. And if you show up at a star party with an 8-inch or larger scope, no one will laugh at you.
And if you can fork out $3000, consider an LX200GPS. I've mostly listed Meade scopes because I know their equipment better, but Celestron makes similar-quality stuff.