Tam has a post up about CAFE standards and econoboxes. CAFE standards are moronic for reasons far more numerous and complex than I'm willing to get into here. As for fun, fuel efficient econoboxes, give me a Mazda 323GTX and I'll be happy.
As for increasing mileage standards, the 2nd comment to tam's post pretty much sums up my thoughts. I mean, if for $25K a car company could make me a 700 horsepower Toyota Supra Hardtop that retains the bulletproof drivetrain and the ability to run around a road course like a bat out of hell and gets 50MPG I'd buy it in a heartbeat. There's a reason no such thing exists, and no amount of wishing it into existence will make it so.