Spent some time last night ping pong pairing with a friend in St Louis. (We're working on a not quite secret project — the Dryer Fluff release of checkr, think lint for Ruby.) He'd write a test, then I'd implement the code to make it work. I'd write a test, and he'd make the code pass. Back and forth over several quick (and a couple of longer) iterations. It was a great way to code. It would have been nice to be colocated with him though, being a couple thousand miles apart is a bit of an impediment to real pairing.
The other cool thing was touching base with zenspider and Eric Hodel on some ParseTree issues while they were at the seattle.rb hacking night.