Like the default Android system clock but wish it could do a little more? Snag an app called DashClock Widget.
Created as a side project by an actual member of Google's Android team, DashClock Widget maintains the basic look of the stock clock but adds in a lot of extra punch. The app utilizes "extensions" to enable functionality like a clock-side display of the current weather, your missed calls, and the number of unread messages in your Gmail inbox. An easy-to-use control panel lets you to activate or remove elements as well as configure a variety of different options.
DashClock Widget is a free download.