I've recently decided it would be fascinating to pick one or two modules out of the New CPAN Modules list every week, and build something small (a couple of hundred lines) around both of them.

If you did that for a year, you'd become quite an adept programmer. You'd also have a good feel for what's on CPAN. merlyn uses this technique fairly well...

That said, there are dozens of modules and programs and projects that run perfectly well on Unix but don't quite make it on NT. If you're itching for some porting arcana, you could start by seeing what errors you get on your machine, and trying to fix them. Initially, you might have to settle for writing bug reports, but eventually you'll be able to submit patches.

(If you're feeling really generous, Jellybean would benefit immensely from that sort of testing.)