JJ posted about a new method he's got of doing mods via a custom firmware that will boot into an x-windows environment. While the intention of the environment is to make mods to theC64's firmware (add games easier), some users have also added additional linux software this environment, so it sounds like a lot of fun.

More info in this thread:

• http://thec64community.online/thread/487/custom-firmware-mod-fel-uart