Take a cheesecake–you spend 5 minutes stirring things up and pitch it in the oven to be ignored for an hour, and people act like you slaved over a hot stove for days. There are a lot of great recipes at Flora’s recipe hideout. The biggest crowd pleaser I’ve found is a basic cheesecake topped with thin-sliced apples topped with cinnamon and sugar that cook/candy as the cake bakes, drizzled with a very small amount of caramel sauce and then topped with crushed Rollo candies. You won’t have to worry about leaving dairy products out in the heat–these always disappear in roughly 2.3 seconds.
Or Irish Car Bomb cupcakes. They’re chocolate-stout cake filled with whiskey-infused ganache and topped with Bailey’s buttercream icing. Sometimes instead of fooling with the cupcake liners and all, I just make it as a layer cake.
Hummus is a great one, too. We can make enough to use up 4 cans of garbanzo beans for a party with 20 or so people, and be scraping the bowl by the end of the night. That’s with everyone having just eaten dinner and us having a bunch of other stuff out. And hummus is cheap and easy and heat stable and compatible with most special dietary needs.
Or if you have a stand mixer you can make marshmallows of any flavor (or a variety of flavors), and set them out with graham crackers and chocolate squares. Somebody will have a grill going, so people can make their own s’mores. Alton Brown has an excellent recipe on the Food Network site, and for flavors just replace the vanilla with some other flavoring/drink/liqueur. Again, you spend about 20 minutes actually working on the things, and people act like you slaved for days.