I use my smartphone for pretty much everything. In fact, I often forget my real camera and have to rely on my phone.
One Good Thing by Jillee has a great list of 49 ways that you can use your phone's camera and they are brilliant - some I already put into practice, others I wish I had thought of. Here are a few that I already use:
Be sure to check out the complete list. How do you use your phone's camera?