An Olympus E-PL2 Pen camera with 75-300mm lens (mounted) and 14-150mm lens next to the Canon EOS 7D with 18-200mm IS lens. That's a zoom range of 28-600mm (equivalent# for the Olympus Pen compared to a zoom range of 28-320mm #equivalent) for the Canon in approximately the same size package. The whole Olympus setup here weighs only a bit more than the Canon body alone. That's not to say that the Pen system performs like the Canon. But if you want to travel really compact and light, I think it's clear, which system is the best.

Olympus M.Zuiko 75-300mm Zoom Lens Review >>
Olympus E-PL2 Pen Review >>