Planypus is a new service that lets you set up a group event or outing without knowing all the details. For example, you can create a "Drinks tonight" plan and send it to a bunch of friends with several different places and times to meet. Your friends pick the options that work for them. You, as the organizer, select the one combination that's best for the group (or for you, depending), and when you press Finalize, everybody gets an update with the plans, which they can import into their calendars.
It's the social counterpart to the business meeting planner, TimeBridge, which looks fantastic but is still in private beta.
The site also has local event listings from StubHub and lets you kick off plans from them. Very handy. What it doesn't do, though, is coordinate the purchase of tickets for everybody or apply a group expense-sharing function the way Buxfer and BillMonk do. Maybe for version 2.
The site is nicely designed, but getting up to speed on the interface took me a few minutes more than I expected it would. My favorite feature: the link that says, "I don't want to be organizer." This is the only event planning system I know of that has a built-in function for dropping the ball.
I'd still use Evite for inviting people to more formal events, such as dinners and parties, but Planypus looks like a really good solution for setting up a group movie night or a spur-of-the-moment outing.