Contacts

Note: Here are some useful links:

Getting Contacts:

http://stackoverflow.com/questions/866769/how-to-call-android-contacts-list

http://stackoverflow.com/questions/6253029/how-to-get-contacts-from-native-phonebook-in-android

http://stackoverflow.com/questions/2205246/how-to-obtain-all-details-of-a-contact-in-android

http://stackoverflow.com/questions/4301064/how-to-get-the-firstname-and-lastname-from-android-contacts

http://stackoverflow.com/questions/5662473/how-to-import-contacts-from-phonebook-to-our-application

http://stackoverflow.com/questions/1588378/android-contacts-extraction

http://stackoverflow.com/questions/4338563/how-to-get-all-android-contacts-but-without-those-which-are-on-sim 

Using Contact Picker:

http://mobile.tutsplus.com/tutorials/android/android-essentials-using-the-contact-picker/

Inserting Contact:

http://stackoverflow.com/questions/4075694/inserting-contacts-in-android-2-2

http://stackoverflow.com/questions/4744187/how-to-add-new-contacts-in-android

http://stackoverflow.com/questions/5151885/android-new-data-record-is-added-to-the-wrong-contact/5158059#5158059

Deleting Contacts:

http://stackoverflow.com/questions/527216/how-to-remove-a-contact-programmatically-in-android