Felt has a new AR bike that incorporates some of the aero traits of time trial and track bikes for a road bike.  I think Cervelo has used some aero designs in ttheir bikes as well.

I'm curious as to why this hasn't been done before.  Aero wheels can be heavier, but faster - why not the bike?

Velonews has a picture of the new Felt AR here. It appears to me that the bike is pictured with Mavic wheels even though Slipstream/Garmin is sponsored by Zipp.