I recently bumped into BCTabBarController, created by Brian Collins, a nice replacement for the UITabBarController. This control is not as tall as the built-in tabbar controller which saves on precious screen real estate. In addition, you can use custom icons for selected and non-selected states.
If you look at the screenshots below, notice there is an arrow pointing upward on the active tab. This control includes a smooth animation of this arrow when selecting a new tab.
Unlike UITabBarController, this control does not support labels. In most cases this is fine and allows for a larger icon, however, this would be a nice addition to the library as an optional feature.
The download from Github also includes a tab.psd file that you can use as a template for creating your own tabbar icons.
Open Source Recommendations ?
Have you written or worked with iOS or Cocoa open source that you think others would find interesting, send me a note.