My favorite carry-all for tools and materials is Festool's Open Top SYS-Toolbox. It's just a classic example of nuts-and-bolts ID: Simple, strong, reliable, and a perfect use of materials. The thick-walled ABS has a channel molded into the bottom, which forms the divider inside the box, and this channel allows the handle of a second box to perfectly nest within the first. Two latches at the side enable you to connect them quickly and securely. And they're compatible with Festool's full line of Systainers (manufactured by Tanos, as we looked at here), making them easy to roll around the shop or carry on-the-go in one piece.
I've got two SYS-Toolboxes—a short one and a tall one—and in one of those rare cases where advertising matches up with reality, I really do use them exactly as shown in the video: