官方：
http://source.android.com/compatibility/index.html#android-compatibility-is-free-and-its-easy
http://source.android.com/source/building.html
Downloading the Source | Android Developers
http://source.android.com/source/downloading.html
http://source.android.com/source/downloading.html#initializing-a-repo-client
http://source.android.com/source/downloading.html#using-a-local-mirror
其他：
http://www.cnblogs.com/fang8206/archive/2011/05/28/2060608.html
http://www.2cto.com/kf/201208/146535.html
http://repository.grepcode.com/java/ext/com/google/android/android/
补充：
http://www.cnblogs.com/hoji-real/articles/2144892.html
http://862123204-qq-com.iteye.com/blog/1992973
http://jingyan.baidu.com/article/c85b7a641200e0003bac95a3.html
http://blog.csdn.net/wh_19910525/article/details/8164107 repo的小结
http://www.cnblogs.com/hongzg1982/articles/2101980.html