This is Canon’s cheapest external flash with a fully swiveling bounce head, which  zooms automatically over a range of 24mm-105mm. Its Wireless E-TTL II compatible too.

This is Canon’s newest and most modern flash unit, with wireless multiple flash system using radio wave communication for enhanced control of up to five groups of flashes.

The SB-700 offers more power for greater depth-of-field control than the built-in flash, and it can be set up as a Commander or a Remote in wireless flash set-ups too. Plus much more.

The SB-910 features Nikon’s i-TTL (intelligent through-the-lens) metering for on camera or wireless flash control, and can operate as a mounted Speedlight, remote unit or Commander.

Wireless flash controller for the Canon 420EX and 550EX and other Canon flashes, which will allow you to take your flashes off camera for more professional looking photos.

This functions as a wireless commander for the SB-R200, SB-900, SB-800, SB-700 and SB-600 Speedlight units, so you can take your flashes off camera for more professional lighting.

This is an awesome alternative to Pocket Wizards, and although this is the Canon version, there’s a Nikon version too. They give you really powerful control at your fingertips.

I prefer Phottix, but Pocket Wizard’s are good too. The FlexTT5 Transceivers gives you full flash exposure control with the freedom and reliability of a PocketWizard radio.

If the off-camera flash options listed here are too expensive for you, then I would recommend a flash sync cable. It allows you to maintain the TTL functionality, at a much lower cost.