Philip Greenspun's on building a digital SLR system and selecting lenses

Philip Greenspun's Weblog. Phil is a great writer and photographer. I liked his pithy summary comment: "[If you don't want to read this article and are impatient to get started immediately, get a Canon Digital Rebel XT and Sigma 30/1.4 lens.]" and this other emphatic opinion:

... The market leader in the professional/advanced amateur photography world is Canon. If you don't have a major investment in lenses you will probably want to buy a Canon digital SLR. The number two spot is occupied by Nikon, which is also a reasonable choice. Fuji and Kodak have made digital SLRs that accept Canon- and Nikon-mount lenses. Once you get beyond Nikon and Canon it becomes very difficult to rent lenses and the companies that make the more obscure systems don't have a large enough market share to invest enough money to build competitive bodies. Leica, Minolta, Olympus, Pentax, and Sigma are the small vendors in the digital SLR market. Unless you have an enormous investment in lenses for one of these brands the only one of these worth considering for purchase is Olympus, due to its innovative Four-Thirds system, discussed below...

I got an XT with the kit lens, and a Canon 50mm 1.8 lens. I think my next lens though will be the Sigma 30/1.4, then after that a vibration-damped zoom if/when Sigma makes one.