My first suggestion is more breakout boards for surface-mount ICs. Currently, there are a couple ICs I’d like to play with, but I can’t find a reasonably priced breakout board for either of them (one is a QSOP24 package, and the other is an HTSSOP38). If SFE had breakout boards available for a wider variety of packages, they would be very useful for prototyping.
My second suggestion is a product that I just discovered today: INCRA rulers. http://www.incra.com/product_markingrules.htm Basically, the ruler has been reinvented. Using these rulers, it is possible to make a much more accurate mark than with a standard ruler. They are available in metric and imperial units as well as a combination of both systems. They can also add a logo if desired. I don’t know what the cost would be like, or how much demand there would be for them, but they could definitely be useful for a huge variety of projects.