My team and I are currently planning to do some Rich Web development for the android and iphone and I am wondering if you guys could share some resources with us. Anything will be welcomed. Thanks in advance.
Take a look at this SO question: http://stackoverflow.com/questions/215390/available-iphone-web-application-javascript-ui-library-frameworks - the answers list off various iPhone web app frameworks, and a useful link to http://distractable.net/coding/iphone-android-web-application-frameworks/. These are all HTML5 based and therefore will work on Android too. There are not any Android specific frameworks that I know of.
Mind you, its debatable if you want to use an iPhone webapp framework that gives native look & feel on Android because the user will have Android device but will have iPhone user experience - which may be confusing.
Have you considered just using something like jQuery & jQuery UI ? iPhone & Android support both of these and they can be used to develop rich apps. Update: http://jqtouch.com/ is jquery based and while I haven't had chance to use it yet, it looks pretty good.
One other thing to bear in mind that users will be accessing your site on limited 2G/3G connections so don't lose track of the download size of your web app.
If you want to "do HTML5" stuff, then I'd recommend that you look at our demos and other stuff at www.sencha.com/products/touch - although if you think jQTouch is overkill, then Touch will definitely be even more overkill [I work for the company]