UI Patterns for Mobile applications. The author even has the book on UI Patterns. The website is good starting point to understand some mobile patterns. Also checkout her blog on this same website.

PhoneGap is an HTML5 app platform that allows you to author native applications with web technologies and get access to APIs and app stores.

SMS Scheduler is an Android application that allows you to schedule a text message to whom you want and when you want. Don't forget to send those important sms anymore!

Android Tapp is the best resource for Android App Reviews, Android Apps, Android News, Android App Ratings, and Interviews with mobile app developers.

A free book on building android apps using HTML , CSS And Javascript.

A good blog to follow about Android apps, phones and news. The author posts good articles, reviews etc.

Use Appcelerator Titanium to create powerful apps with native controls using the Web technologies you know. Learn what makes Titanium-based apps irresistible.

This tool was written to make my Java programming life easier. It can be used to build graphical user interfaces for the Android cell phone platform.

A very active forum website for Android Developers. It has got some good discussion and tutorials too.

You can build just about any app you can imagine with App Inventor. Often people begin by building games like WhackAMole or games that let you draw funny pictures on your friend's faces.