I recommend the late-model Honda Civic. 40+ mpg, most of the amenities we used to associated with luxury cars, and a price roughly in the 20k range for a new one.
2008 Accord EXL and 2012 Civic EX, both great cars!
Accord on trips 34/35 MPG, Civic on trips 43+/- MPG in ECON mode.
http://autos.yahoo.com/consumerreports/