If you're not lucky enough to be an Apple developer and to have sprung for a US$1,500 badge for WWDC you can keep up with the Stevenote as it unfolds online. True, there's no Webcast or video stream, but there are about a dozen blogs that are covering the keynote address in every manner of text.
The WWDC Keynote Kit is a simple application that opens all the major sites that are covering WWDC in tabs in your Web browser. It works better in FireFox and Flock so if you're using Safari read about the workaround first. Check it out!