If you work in a cubicle chances are you already have push pins stuck in the fabric walls. Reddit user KayJustKay demonstrates how you can use a handful of push pins to provide an impromptu dock for your phone.
The only problem with this method is that if you make a lot of calls on your mobile phone while at work you'll be taking it in and out of the "dock" all day long. Since I use Google Voice to forward calls to my phone to my office phone during work hours this isn't a problem for me, but it's worth considering. I also like how it keeps your phone off your desk so you don't have to worry about burying it under reports.