The Android SDK contains lots of useful icons, which you can reuse in your application. The Android team does not want you to link to some of them directly, as they might change in a future version and your icons should be static. Therefore you have to copy them into your application drawable folder.
For example if you are looking for a nice refresh icon you could use: path_to_android_sdk\platforms\”android-xx”\data\res\drawable-hdpi\ic_menu_refresh.png.
Whereby you replace xx with the version of the Android SDK you are interested in.
I hope this helps.