I get a lot of questions about resources for learning how to use speedlites. Lighting with small flash is a hugely popular subject. As an example Scott Hargis's post on Interior lighting with multiple strobes, is the most popular post on this blog. The only page, other than the front page that gets more traffic is the real estate photographer directory.
So, when I ran across Syl Arena's site speedliting.com I thought I'd pass it on. Syl does a couple of kinds of workshops and has a ton of great small flash content on the site. As indicated in the site's subtitle "Learn Canon Flash Photography", the site is Canon oriented but Syl pointed out on This Week in Photography that 80% of his site's content and tutorials applies if you are shooting with any brand of equipment.
While I'm at it here is a list of other of the resources for learning to light with small flashes:
Small flash lighting is popular for use in real estate photography because it minimizes the amount of lighting gear you have to carry and thus the amount of setup time required. Speed is an issue in real estate photography because you are typically expected to shoot a home in a couple of hours or under. Frequently the agent you are working for has to let you in the home and is waiting for you.