Strobist.com blog is a fantastic resource for anyone using portable strobes (your camera flash guns or speedlights if you own a posher camera) as their primary light source, or wants to explore their creative use.
They maintain a fantastic beginners resource document called Lighting 101 which has now been updated and is available to download from this link.
The site is very US-centric in a lot of the products they advertise or recommend , but the basic knowledge base and contributed examples make up for this. The How-To’s of lighting layout and techniques are worth the effort and the numerous examples provide endless inspiration.