There is a working group called the Web Hypertext Application Technology (WHAT) Working Group that is working on some really interesting extensions to the HTML / XHTML specification for submission to the W3C. Their goal is to extend the Form specification to better support Web applications. JD mentioned this briefly and it’s been mentioned in other blogs recently, but I think it is worth the time for developers to read the actual working documents and provide their input to what could be a major change to the HTML / XHTML specifications.
Much of what is being proposed would make the browser capable of rendering HTML forms with input capabilities more like those already found in Flash forms (embedded .swf files). I think that the key to this working would be strong backward compatibility, if we see a generation of web forms that break in relatively modern browsers (say one major version behind the latest release) it would be very bad for everyone. On the positive side, if even a few of the recommendations, such as a the calendar element or changes to the form element, are made a part of the standard and supported in browsers it would be great for developers and users.
I look forward to seeing this idea grow and spread.