The W3C have released their mobileOK Basic 1.0 Tests as a Candidate Recommendation (that is a draft standard). These are tests intended to see how compatible web pages are with mobile phones and other hand held gadgets. The aim is "Making Web access from a mobile device as simple, easy and convenient as Web access from a desktop device". As well as the test specification document, W3C have provided some very useful software implementing some of the tests. A press release has background on the project.
I have tried out the tests and found them very useful, even where the web pages were not specifically targeting mobile devices. My only quibble is that perhaps the W3C's Mobile Web Best Practices Working Group should run the tests on their own web pages. ;-)