Automate Your Android with Tasker

"What if your phone automatically went silent when you step into the movie theater? Texted your significant other when you finished your long commute? Or automatically turned down the volume when a particularly loud friend called? It can; here's how."

I recently purchased Tasker, and have started adding my own tasks.  My favorite task so far is checking when I am at work - silencing my phone and forwarding calls to my desk.  This app can do everything you can think of and more, but can be a little tricky to get the hang of at first.