Saw this design recently: http://www.redmaloo.com/ but two things immediately struck me, no handle and no where to store a power supply or mouse. So....
Note: as of 9/12 The bag is complete but havent added pockets for psu, mouse & bateries
Step 1: Materials
Materials are irrelevent. Although the felt case from the Maloo site may cause some cooling issues for powerbooks. I wanted a moderately durable material and opted for this 1/8" thick antistatic workbench rubber mat. Some neoprene for the interior to provide some shock absorbsion and a combination velcro & tarp snap for fastning.