I did a TT on a regular road bike last year and averaged 22.5 mph over a moderately hilly 12 mile course. The winner on a TT bike was in the 27s.

I did an A group ride in flat FL this summer and the first hour average was 24.2 mph. I was dropped shortly thereafter for the long, lonely ride home. It's amazing how quickly the group pulls away once you are dropped.

Fastest commute one-way was 19.8 mph for 15 miles on my road bike, but normal commute is in the 17-18 mph range on my commuter bike.