I've created a set of Max objects for working with the Launchpad (manipulating LEDs and getting button presses). They basically just implement the functionalities described in the Launchpad Programmer's Manual. Max help files are included for the objects.
These are built for straight up Max - I don't have Live or M4L so I don't know how this would work in that environment.
Although there are probably lots of similar things out there, I haven't seen any well-documented Max objects for the Launchpad. I'm working on a "smarter" Launchpad renderer soon, which will set LEDs more efficiently, handle brightness better, and prevent the Launchpad from freezing up when you send it too many messages.
Comments and bug reports are welcome!