Cross-OS platforms for mobile development on the whole are not yet a completely perfect, have-your-cake-and-eat-it-too solution, but many of them offer an excellent alternative to ignoring one mobile OS in favor of another or, perhaps worse, burning serious resources to develop for two or three platforms at once.
AppAccelerator
JayData
JayData was launched in 2012 to provide a standard, cross-platform library and method to access and manipulate data from various sources. JayData is at its best when used for multi-platform applications with HTML5 and JavaScript.
Mobello
QuipoJS
QuipoJS is a minimalist, modular and object-oriented Javascript library with a goal of only 8-12k. It allows you to write powerful, flexible and cross-browser code with an elegant, well documented and micro coherent API. You just have to concentrate on getting stuff done.
XUI
Sencha Touch
Sencha Touch, a high-performance HTML5 mobile application framework, is the cornerstone of the Sencha HTML5 platform. Built for enabling world-class user experiences, Sencha Touch is the only framework that enables developers to build fast and impressive apps that work on iOS, Android, BlackBerry, Kindle Fire, and more.
Moobile
AppGyver
stacktable.js
The-M-Project
The-M-Project is a Mobile HTML5 JavaScript Framework that helps you build great mobile apps, easy and fast.
DHTMLX Touch
DHTMLX Touch is a free open source JavaScript library for building HTML5-based mobile web apps. It’s not just a set of UI widgets, but a complete framework that allows you to create eye-catching, robust web applications that run on iOS, Android, and other mobile platforms.
WebApp.Net
WebApp.Net is a light weight, powerful javascript framework taking advantage of AJAX technology. It provides a full set of ready to use components to help you develop, quickly and easily, advanced mobile web applications.
PhoneGap
Easily create apps using the web technologies you know and love: HTML, CSS and JavaScript. PhoneGap is a free and open source framework that allows you to create mobile apps using standardized web APIs for the platforms you care about.
ApplicationCraft
ChocolateChip-UI
ChocolateChip-UI has been completely rewritten to abstract out the differences between ChocolateChip.js, jQuery and Zepto. There is now only one version of ChocolateChip-UI. It is exactly the same for all three libraries. This means you get the exact same feature set, functionality and behavior, regardless of the library you use. ChocolateChip-UI has been updated to work with iOS versions 5 and 6, and Android versions Icecream Sandwich and Jelly Bean.
Dojo Mobile
Dojo Mobile is a world class HTML5 mobile JavaScript framework that enables rapid development of mobile web applications with a native look and feel on modern webkit-enabled mobile devices such as iPhone, iPod Touch, iPad, Android and RIM smartphones and tablets.
iUI
iUI is a framework consisting of a JavaScript library, CSS, and images for developing advanced mobile webapps. Made with only iPhone in mind in the first place (reason of i UI), it now supports most smartphones & tablets.