We're each currently running with a pair of panniers with each pair having total capacity of 56 litres. I have a tent and groundsheet, plus my croc knockoffs and the bike lock on the rear rack. I have a handlebar bag on the front. Machka has a Carradice Nelson longflap across the rear rack, and a smaller handlebar bag that I.
My current weight is around 46-3/4 pounds (21.2kg). That includes a netbook computer plus associated charger, a video camera with two high capacity batteries, and 5-1/2lb three-person tent. It's probably at the limit of what is appropriate to handle as far as the extensive airline travel we are undertaking. We've already paid weight penalties on one airline, although we did take this into account with our budgeting.
There also are the additions that will inevitably go into the load, including paperwork, and the occasional souvenir. There is still room to pack food.