My boyfriend travels with a Thinkpad and a Powerbook.

The biggest challenge was finding a bag to hold them. The Brenthaven Backpack designed to fit the 15" Titanium Powerbook holds two laptops securely, one in the sleeve that comes with it, and one in front of that. There are plenty of standalone sleeves you could get to insert in there if you want each to be protected. With both put away, there's still room for cables, dongles and other accessories.

Timbuk2 might be another option. They have some jumbo sized bags. Their laptop bag offerings are not as appealing as they once were, however, after moving much of the manufacturing to China and revving their product line. Also, these aren't as professional looking.

Don't throw your back out lugging those machines around!