A list of my favorite sites:
BikeExif
Bike Metric
Boxer Works
Bubblevisor
Dime City Cycles
El Solitario MC
Fotoduda
Garage Project Motorcycles
Le Container
Motart
Moto Mucci
Otto Nero
Pipeburn
Return of the cafe racers
Roel Scheffers
Sakeracers
Silodrome