Few things are as unpleasant as dropping a chain onto a new frame's bottom bracket shell, but one that comes to mind is dropping a chain under power, which is like the first one, only extremely painful. The 14g 3rd Eye Chain Watcher adjusts to fit 1-1/8-inch to 1-3/8-inch seat tubes and keeps your chain on your ring.
Add some protection from nicks and scratches to your road frame with Lizard Skins' Chainstay Protector.
Keeping your chain in place on a single chainring doesn't get any simpler or more elegant than the 68g Chain Keeper.
*Orders received before 3:00PM Pacific time are shipped the same day (M-F). Orders over $100 are shipped free (USA only, excluding AK and HI). Some exceptions apply. See Shipping for details.