Using flash for portrait photography is something that scares a lot of photographers, but once you master it, you will wonder how you ever worked without the complete creative and technical control it offers. If you are just starting out and unsure of how to get rolling, check out this fantastically comprehensive video tutorial that covers everything from the different types of flash through to how to use TTL and complex multi-light setups.
Coming to you from Ed Verosky, this awesome video tutorial will show you everything you need to know to get started working with flash for your portrait photography. By far, the most important bit of advice I would give budding strobe users is to keep it simple at first. A lot of people try to jump into using complex multi-light setups right off the bat and end up overwhelmed by trying to wrangle them all simultaneously before they have mastered the fundamentals of light's properties and behaviors. And don't worry, you can still make high-quality images using a single light; professionals do it all the time, in fact. Once you've mastered that, you'll feel much more comfortable moving on to using two and three lights. Check out the video above for the full rundown from Verosky.
Good and comprehensive article. Most beginners and amateurs rely on their speedlite on the hot shoe. When taking group or family images using the speedlite on the hot shoe, I find using a diffuser is very helpful. I carry one (G. Fong's Lightsphere) with me, works great, and is part of my camera bag inventory.
Complete and informative overview of lighting.