Mobile Development & Phonegap related

Javascript libraries:

From http://www.adobe.com/devnet/phonegap/articles/phonegap-apps-powered-by-developercom.html

Reuse Existing Tools

Since PhoneGap applications leverage Web technologies, there are countless existing libraries or frameworks that you can leverage to accelerate application development. Whether it is a solution accelerator framework like jQuery or Zepto, a UI toolkit like Twitter Bootstrap, jQuery Mobile, or Sencha, or a data visualization library like Raphael.js, Highcharts, or RGraph.js, there are lots of resources both open source and commercially that you can leverage within your applications.

Solution Accelerator Frameworks - jQuery, Zepto
UI Toolkits - Twitter Bootstrap, jQuery Mobile, Sencha
Data Visualization Libraries - Raphael.js, Highcharts, RGraph.js

3rd party Database options:

1. Parse.com -
http://www.adobe.com/devnet/phonegap/articles/using-parse-with-phonegap-a-marriage-made-in-awesome.html - Dec 2012

2. Database.com -
http://www.adobe.com/devnet/phonegap/articles/phonegap-apps-powered-by-developercom.html - June 2012

Push Notifications:

Below plugin allows the App to receive push notifications on both Android and iOS devices:
https://github.com/phonegap-build/PushPlugin
Tutorial - http://devgirl.org/2013/01/24/push-notifications-plugin-support-added-to-phonegap-build/

Above github link also mentions a Ruby Gem called "pushmeup"  (See section titled "Test Environment")
(Use - to push notifications directly from your desktop during development)

Phonegap:
 https://github.com/phonegap/phonegap/wiki