I've also been playing with PICAXE microcontrollers again. Here is a pair of routines that can be used to get/send bytes using the TI hardware link protocol, for example. I am yet to do anything useful with them, however.
Windows programming has never been my favourite side of things, but I have also started work on a Z80 ASM "IDE" called Latenite:
Clicky
It's mostly there, but now needs features galore to be added. So far it can be used to compile and source code, which is the main thing.
You could also try out GBA development. I haven't done much on it, but it seems pretty entertaining and it is still can be considered a modern platform for game development.