I bought two radicchio heads at the farmer's market. Is there anything to do with them besides mix in a salad with other greens?

Granted, this is a salad, but it uses farro, dried cherries, and blue cheese to go with the radicchio:
http://www.oregonlive.com/foodday/index.ssf/2008/06/recipe_detail.html?id=8121

You can also braise them on the stovetop in stock and wine (add a bay leaf). After cooking them, remove to a plate, reduce the sauce, and add a splash of cream at the end. Serve with toasted buttery bread crumbs

I chop it up and cook it on pizza with pears and some blue cheese. stilton please!

par boil the heads and gently peel the leaves apart. Spread individual laves on a baking sheet and drizzle with oil. Season with salt, pepper and whatever else... the use the "crisps" like chips or toasts.

Peel the leaves, stuff and roll with goat cheese, grill and serve.

How much time do you have...? I just made this for a party and it was amazing. Radicchio wasn't exactly the star but it was a key player, and my husband and I snacked on the roasted radicchio as we assembled the lasagna (luckily we had extra...!). http://www.nytimes.com/2011/11/27/magazine/gooey-wild-mushroom-lasagna.html

I second the idea of roasting. Sprinkle them with parmesan too! They also make an excellent salad all on their own, without other greens mixed in. Use strong, salty, and sweet flavors to stand up to them. I love a radicchio and radish salad with an anchovy vinaigrette. Some chopped boiled egg wouldn't hurt either.

Cut off the root end, separate the leaves, soak for 5 minutes in cold water to reduce bitterness. Proceed to make a salad, shave over fish tacos, enjoy!

I love them grilled/roasted like MarcusV described.

Quarter, drizzle with olive oil and salt, and roast in a 450 F oven until caramelized. Splash with balsamic before serving.