A very versatile and often overlooked tool that can cost next to nothing is a simple TTL cord. With this cord you can get your flash off of your camera and still maintain your flash and camera communication.
One great trick that you can manage with a TTL cord involves High Speed Sync and a TTL flash unit. There are many companies out in the market that offer TTL flash units for the major camera brands and for the most part they are very capable and affordably priced.
