The Knoppix CD edition has a little problem with disk space, mostly caused by well-meant suggestions about useful programs to include. Software tends to continuously grow, so, since the CD is already full with 1.8GB of software (compressed, physical space 700MB), I have to remove some software on every new release. This is sad, because once you got used to a program, even if it is "just a game" for testing the graphics and sound capabilities of new hardware, you will miss it once it is gone, and of course many people complain if their favorite program is gone in a new release. Fabian Franz, author of some of the packages on Knoppix, is currently working on a modularized version of Knoppix, based on Debian meta packages and Knoppix-specific packages. So, you could use a build system to build your own version and include just the packages you want.