Cross-platform development with WPF/E
I love mac, I love mac, I love mac, I love mac, I love mac. Alright, it's not true, but this is what I have to keep telling myself to trick myself into developing for the mac.
I'll be playing around with WPF/E for a while to see what kind of cool apps I can develop. I think Microsoft's move to develop a flash alternative is 100% the right direction.
So far, my experience with the G4 that Erik Chapman has loaned me makes me realize that Windows is years ahead of Mac OS, but I have yet to immerse myself in the OS, so maybe it'll just take a couple days - *ahem*, weeks.