We already have a discussion group (this one here) about multi platform installs (not limited to InstallShield).
Would you also like to have a section with samples, beans, tips, etc.?
Currently there is a page with samples for the previous InstallShield Java Edition (under Other IS Tools), and it's not much activity there. I'm currently not using IS-MP myself, so it would be up to you to send me content.
Please post your votes here.