Developing apps for both iPhone and Android

Check out PhoneGap

PhoneGap allows you to develop apps using HTML, CSS and Javascript for a range of mobile devices

http://www.appcelerator.com/

http://www.sencha.com/products/touch/

and PhoneGap is good too

You can use a mix of cross-platform HTML5/Javascript for the web-ifiable (in looks and performance) UI parts of the app, and plain ole C (which is both a subset of Objective C, and available in Android through the NDK) for the OpenGL/data/number crunching parts with high performance requirements. The native UI parts may just have to be redesigned for the native platforms and (re)written twice.