[Android] Project Layout

Core Project: foundation of the Android platform
hmtsay@ubuntu:~/android$ ls
bionic    cts          device      hardware  ndk       prebuilt
bootable  dalvik       external    libcore   out       sdkbuild     development  frameworks  Makefile  packages  system

[] http://sites.google.com/a/android.com/opensource/projects
cts: Compatibility Test Suite
   []http://source.android.com/compatibility/cts-intro.html
device:
kernel: No (separated Android from Linux kernel)
libcore: ?
ndk: Provide tools and documentation for developers to create native code shared libraries.
out: Compile results? (see PS)
sdk: Provide tools, sample code, and docs for developer to create great applications.

External Project: Android makes use of many other open source projects
hmtsay@ubuntu:~/android/external$ ls
apache-http  elfutils    ipsec-tools     netperf   srec
astl         embunit     iptables        neven     stlport
bison        emma        jdiff           opencore  strace
blktrace     esd         jhead           openssl   svox
bluetooth    expat       jpeg            oprofile  tagsoup
bsdiff       fdlibm      jsilver         ping      tcpdump
bzip2        freetype    jsr305          ppp       tinyxml
clearsilver  fsck_msdos  junit           proguard  tremolo
dbus         genext2fs   kernel-headers  qemu      v8
dhcpcd       giflib      libffi          quake     webkit
dnsmasq      grub        libpcap         safe-iop  wpa_supplicant
dropbear     gtest       libpng          skia      wpa_supplicant_6e2fsprogs    guava       libxml2         sonivox   xmlwritereasymock     icu4c       mtpd            speex     yaffs2
elfcopy      iproute2    netcat          sqlite    zlib

Packages: standard Android applications and services
hmtsay@ubuntu:~/android/packages$ ls
apps  experimental  inputmethods  providers  wallpapers
hmtsay@ubuntu:~/android/packages$ ls apps/
AccountsAndSyncSettings  CertInstaller  Launcher2         QuickSearchBox
AlarmClock               Contacts       Mms               Settings
Bluetooth                DeskClock      Music             SoundRecorder
Browser                  Email          PackageInstaller  SpeechRecorder
Calculator               Gallery        Phone             Stk
Calendar                 Gallery3D      Protips           VoiceDialer
Camera                   HTMLViewer     Provision
hmtsay@ubuntu:~/android/packages$ ls providers/
ApplicationsProvider  DownloadProvider        MediaProvider
CalendarProvider      DrmProvider             TelephonyProvider
ContactsProvider      GoogleContactsProvider  UserDictionaryProvider

PS. out/: compile results
hmtsay@ubuntu:~/android/out$ ls
casecheck.txt  CaseCheck.txt  host  target  tmp  versions_checked.mk
PS. The system image of Android 2.2 Froyo is about 60MB. 
hmtsay@ubuntu:~/android/out/target/product/generic$ ls -l -a
total 60064
drwxr-xr-x  7 hmtsay hmtsay     4096 2010-10-04 07:52 .
drwxr-xr-x  3 hmtsay hmtsay     4096 2010-10-04 05:51 ..
-rw-r--r--  1 hmtsay hmtsay        7 2010-10-04 07:52 android-info.txt
-rw-r--r--  1 hmtsay hmtsay     1160 2010-10-04 05:51 clean_steps.mk
drwxr-xr-x  3 hmtsay hmtsay     4096 2010-10-04 06:20 data
-rw-r--r--  1 hmtsay hmtsay    16134 2010-10-04 07:52 installed-files.txt
drwxr-xr-x 13 hmtsay hmtsay     4096 2010-10-04 07:44 obj
-rw-r--r--  1 hmtsay hmtsay       50 2010-10-04 05:51 previous_build_config.mk
-rw-r--r--  1 hmtsay hmtsay   166468 2010-10-04 07:52 ramdisk.img
drwxr-xr-x  8 hmtsay hmtsay     4096 2010-10-04 06:21 root
drwxr-xr-x  4 hmtsay hmtsay     4096 2010-10-04 06:21 symbols
drwxr-xr-x 10 hmtsay hmtsay     4096 2010-10-04 07:35 system-rw-------  1 hmtsay hmtsay 59794944 2010-10-04 07:52 system.img-rw-------  1 hmtsay hmtsay  1482624 2010-10-04 07:52 userdata.img