I have certainly seen wide format 17" displays on the market, but most are designed to support signals from the computer as well as from TV. As a result, they tend to be a bit more expensive and have lower resolution than their 4:3 counterparts. If you are still interested, I have seen widescreen versions from Sharp, Viewsonic, Phillips and even (gasp!) Dell. When dealing with LCD displays, though, remember that quality does vary between the manufacturers. Also, be sure to consider how you are going to connect this new display to your computer. The picture will be much sharper If you have a digital connection than if you use the analog VGA port. If you have a newer mac (within say the last 3 years), then you probably have ADC (a proprietary digital connection) and VGA ports. You can easily convert from ADC to DVI with an attachment, but it's an added expense (not major though).
I would try CNET for buying advice and to screen products. With a display, though, it is probably useful to go to a store (if they have the screen you are interested in) and look at the picture first.
Andrew