The Keurig K-cup is not exactly a pod system, but they do sell their own refillable filter. It seems lots of companies make K-cups with a variety of coffees. I haven't looked at these until just now.
I've been looking at the semi-automatic espresso machines because my daughter wants one, so I wanted to know what's so special about espresso makers. Some of these take "ESE espresso pods", which
are different from the other 'pods'.
For myself, I've been using a Melita-style cone with a Black&Decker Brew-'n-Go; pretty quick, not much mess using paper filters, and decent enough, if not espresso
Oh, and cheap, too, about $25 for the B&D.