One of my favorite Federal agencies. From everything I've heard, a great place to work, both in the field and at HQ.
I wish there was a "Peace Corps-Lite" where you spend 6 months digging ditches in Eastern Africa. Two years off the grid is too beaucoup. Though if I was, say, 21 and just graduated college would seem like fun.
There are "Peace Corps Response" positions which are for as few as ~three months. You have to be a specialized professional in something they're looking for, though; I'd guess mostly healthcare.