Shortcut to change the keyboard layout

I quite often switch between 2 different keyboard layouts for various reasons. So far, I just changed via the flag icon in the menubar.

After having used Windows for many years and just having switched to Mac recently, I do miss the Alt-Shift (or Control-Shift, or Alt-Control-Shift) shortcut to change between keyboard layouts.
I'm certain there is a way to make this possible on the Mac too, but how?
Quicksilver? System Preferences?

I'd appreciate it if somebody could help me out.