Do any one know how to develope App for Android ?

Sure XRok - what sort of thing you thinking of?

If it's a productivity type app (tables, checkboxes, data etc) then it's worth looking at a cross-platform dev stuff, i.e.

http://xamarin.com/monotouch

http://www.appcelerator.com/

If it's more game/graphical then there's the base SDK from Google

http://developer.android.com/sdk/index.html

..or more custom kits with some nice libraries i.e.

http://www.coronalabs.com/

http://unity3d.com/unity/publishing/android

Sort of depends on what stuff you've developed before and what you have in mind. Hope that helps.