Really nice new Mac app by Surtees Studios: Bartender is a menubar app to hide other menubar apps. Providing its own custom bar to collect other icons from third-party apps, Bartender lets you organize your menubar apps while retaining the functionalities they come with. The app automatically finds third-party apps running in the menubar; it allows you to completely hide them, or show them in the Bartender bar. If you choose the latter option, your menubar apps will stil remain fully working with popover windows and keyboard shortcuts. I installed Bartender and I am using Fantastical and Delibar just fine; I only noticed a minor visual glitch with Take Five, and I believe the developers are adding support for more apps as we speak.
Furthermore, Bartender lets you assign a keyboard shortcut to the custom bar, and it even allows you to revert back and “show all menubar apps” with a separate hotkey. The Bartender bar can be placed anywhere at the top of the screen, and you can set apps that update (such as Sparrow’s menubar icon) to be shown in the regular menubar for only five seconds.