We've noted before that more megapixels don't mean a better camera; a better indicator of photo quality from a camera is its sensor size. The Sensor-Size app helps you compare popular cameras' sensor sizes and also convert unfriendly ratios often given.
Many point-and-click cameras often report their sensor size as a ratio, e.g. 1/1.8 inches, or in millimetres, making it hard to compare different cameras. Sensor-Size's calculator will get you the simpler diagonal measurement — the larger the measurement, the higher photo quality you can expect from that camera.
The site also offers a table that compares sensor size and other features of best-selling digital cameras. As you'd expect, digital SLR cameras like the Nikon D300 DX and the Canon EOS 40D have very high sensor sizes. There are also a few compact cameras with above average sensor sizes, like the Panasonic Lumix DMC-LX5 or the Fujifilm FinePix F200EXR.
If you're in the market for a new camera, check out the site before buying.