SLAX Live CD ( http://slax.linux-live.org/download.php
) is fairly easy to customize.
All the programs installed at boot are .img files and all are stored in a folder /SLAX/modules. Using some .iso editing software you can add and remove modules and burn custom cd's for diff applications. It's small too. I think under 300meg.
If your burning in windows magicISO ( http://www.magiciso.com/
) is what I used. It's free but has a burn limit of 300meg or something like that unless you buy it.
Give SLAX a try. If you don't like, well, you have another coaster for your coffee...