Designing App Tab bar.

http://ericharlow.blogspot.com/2010/09/experience-multiple-android-activities.html?showComment=1320054869021#c2304244239855411185

Handling Threads in different ways in Android

Plz follow this link  http://www.vogella.de/articles/AndroidPerformance/article.html

15 best social networking Android Application designs


http://www.web-designers-directory.org/articles/15-best-social-networking-android-applications-21.html

Seek bar animation



http://www.java2s.com/Code/Android/Core-Class/ThisapplicationdemonstratestheseekingcapabilityofValueAnimator.htm

Sending E-mail:

Text:
http://mobile.tutsplus.com/tutorials/android/android-email-intent/

Image:
http://mobile.tutsplus.com/tutorials/android/android-sdk-sending-pictures-the-easy-way/