"the possibilities are endless"
only time isn't...
There are many different output devices as Neil has showed. You have to keep in mind the amount of memroy your chip has. You cna make a bogus program with the libraries you intend to use and check if that fits on your microcontroller. Probably the biggest part of your code will be the libraries...
Most of the stuff that neil has showed is in the electronics corner, but you'll have to look; we do not have everything.
For me the interesting parts would be - eInk screens (maybe from the SHA badge...) But Henk thinks it is to difficult. So I'll stick with the - LED's; maybe make my own RGB LED: these could be enough colour to make the clock I want..
So: for this week I am going to make my own PCB that drives an RGB LED.
Exciting? No... but for fuck sake, it would be nice to finish a project some time... ¯_(ツ)_/¯