I'm 99.99% sure it is the Minimalistic Text widget. I use it sometimes as well. It's pretty awesome, but takes a bit of tinkering to figure out the settings, etc.
I used another Simple Calendar widget with a transparent black background (and hiding everything else) to achieve the right column background effect. My only problem with this set up is that the widgets don't really line up perfectly, which may or may not bother me over time.