Was playing around with jquery mobile the other day, which has planned it's first beta release sometime next week.
jQuery mobile is what jquery+jquery-ui are to desktop browsers. It abstracts a lot of the parts away so that you can write your code without having to figure out all the different mobile browser quirks yourself. It offers a structure to make web apps which are cross platform across current mobile devices and which as a bonus work in desktop web browsers as well.
Mobile style events are provided as well. Like touch and swipe which work across the various mobile browsers is a nice touch.
Another great thing it provides is media queries. CSS media queries are buggy on some browsers so this abstracts out a lot of the bugs on the various different devices.
Supported are most of the mobile devices. Some are supported better than others, and some provide certain features that others do not provide. For example, the ajax style page loading is not done on opera mini. But works on android, and safari mobile browsers.
I'm quite looking forward to the feature complete beta release. It's been a long time baking, and smells quite nice.