Android Versions...

1 Android beta ( 2007 November)
The first released Android version.


2 Android 1.0 (2008 September)
 The first relased commercial version.First Android device HTC dream ran this version.

3 Android 1.1(2009 February)



4 Android 1.5 Cupcake (2009 April)
First used the desert nickname.


5 Android 1.6 Donut (2009 September)



6 Android 2.0/2.1 Éclair (2009 October)


7 Android 2.2.x Froyo(2010 May)


8 Android 2.3.x Gingerbread (2010 December)


9 Android 3.x Honeycomb (2011 February)
 The first tablet android update.


10 Android 4.0.x Ice Cream Sandwich (2011 October)

Samsung Galaxy Nexus running Ice Cream Sandwich.

11 Android 4.1 Jelly Bean (2009 July
The latest version.

I took all these infomation from Wikipedia(Big thank for those contributors) and summarized.  If you need more details , pls see http://en.wikipedia.org/wiki/Android_version_history