I attended the WDC2011 conference last week in Bristol, England where Rob Hawkes, Mozilla Evangelist, gave a great talk about HTML5. One of the Mozilla efforts that Rob spoke about is the WebAPI. This is a group of Web APIs that will be used to create an HTML5 “operating system”.
Many of the APIs Mozilla is working on to create an HTML5 phone experience fall under the Device API working group of standards at the W3C. There is a ton of great information at this site, and lots to learn about what’s being developed. Also check out the Mozilla blog post introducing the API development there.
This is very cutting edge stuff, and you won’t be able to use most of it for quite a while to come, but if you’re interested in building mobile web apps, keep an eye out on the WebAPI and the Device API development.