Where can I see my friends' listening activity on Pandora?

Ah, great question Chase. I'm pretty sure we have more or less what you're looking for.

Below the music player, on our home page, is an "Extras" box with lots of information you can peruse.

If you click on "Your Profile" in the Extras box you'll see three options: Bookmarked Songs and Artists, and at the right, Friends.

If you click on Friends you'll see the people you've bookmarked, their listening status, and what they've listened to and bookmarked recently.

If they're currently listening, the person icon is blue. If they're not currently listening, their person icon is gray. You can even leave a profile comment for the person directly from that box.

(Also, when you look at people's full profiles, if they're currently listening, it will say "Now Listening to..." and list the station.)

If you use our application on Facebook, bookmarking and listening information shows up in the mini-feed, so if your friends are using the app too, you have a nice view into what everyone is doing on Pandora.
http://apps.new.facebook.com/pandora/

Let me know if this helps, or if you have comments!

Cheers, Lucia