What's the best way to develop a sideswipe menu like the one in Facebook's new iOS app?

There is a great library for this by Tom Adriaenssen: Inferis/ViewDeck

It's very easy to use and has a fairly large following.

EDIT:

For something a little more lightweight, check out: mutualmobile/MMDrawerController

It doesn't have all of the features of ViewDeck but is simpler to modify and extend.

I created a library for this. It is called MFSideMenu.

Among other things it includes support for iphone+ipad, portrait+landscape, menu on the left or right side, UITabBarController, and pan gestures.

I recently came across this, didn't actually look at the code or test the control, but looks like it may be a very decent starting point.

jtrevealsidebar

Edit: The reader should also take a look at the other answers :)