If you're not using the launcher that came with your phone's version of Android, chances are you're either using ADW Launcher or Launcher Pro. Launcher Pro may not be open-source like ADW is, but it includes some enviable features. This is not the total re-write that dev Federico Carnales blogged about a few days ago, but it is still an upgrade worthy of a new decimal increase.
Besides bugfixes, this latest update brings another cool trick to the table, specifically swipe-up pop-ups in your launcher's dock which show details of relevant notifications. Currently there is support for missed calls and unread SMS, but more will appear in later versions.