Please take a look at Android forum. Also, this is a list of links ( I did it for myself some time ago ) to create Android development environment:
...
// Android Related Links
// http://developer.android.com

+ JDK6 : http://download.oracle.com/otn-pub/java/jdk/6u31-b05/jdk-6u31-windows-i5...

+ Android SDK : http://dl.google.com/android/android-sdk_r17-windows.zip
+ : http://dl.google.com/android/installer_r17-windows.exe
+ : http://dl.google.com/android/android-sdk_r18-windows.zip
+ : http://dl.google.com/android/installer_r18-windows.exe
+ : http://dl.google.com/android/android-sdk_r20-windows.zip
+ : http://dl.google.com/android/installer_r20-windows.exe

+ Android NDK r7b : http://dl.google.com/android/ndk/android-ndk-r7b-windows.zip
+ Android NDK r8 : http://dl.google.com/android/ndk/android-ndk-r8-windows.zip

+ Eclipse Classic 3.6.2 : http://www.eclipse.org/downloads/download.php?file=/eclipse/downloads/dr...
+ Eclipse IDE for C/C++ Developers: http://www.eclipse.org/downloads/download.php?file=/technology/epp/downl...

// JDK6 : http://download.oracle.com/otn-pub/java/jdk/6u31-b05/jdk-6u31-windows-i5...
+ Windows x86 (32-bit) 78.98 MB jdk-6u31-windows-i586.exe
Java SE 6 Update 31 / JRE alone is not sufficient
http://www.oracle.com/technetwork/java/javase/downloads/index.html[/embed]

// Android SDK : http://dl.google.com/android/android-sdk_rXX-windows.zip
http://dl.google.com/android/installer_rXX-windows.exe

+ Starter Package
http://developer.android.com/sdk/index.html

// Android SDK Tools r27: http://developer.android.com/sdk/tools-notes.html
-

// Android NDK r7b : http://dl.google.com/android/ndk/android-ndk-r7b-windows.zip
+ http://developer.android.com/sdk/ndk/index.html

// Eclipse 3.6.2 Helios :
+ Eclipse Classic 3.6.2 :
http://www.eclipse.org/downloads/download.php?file=/eclipse/downloads/dr...

+ Eclipse IDE for C/C++ Developers:
http://www.eclipse.org/downloads/download.php?file=/technology/epp/downl...

// Eclipse JDT : http://www.eclipse.org/jdt
- Included in most Eclipse IDE packages

// Eclipse ADT : http://developer.android.com/sdk/eclipse-adt.html
-

// Apache Ant 1.8 : http://apache.mirror.nexicom.net//ant/binaries/apache-ant-1.8.3-bin.zip
- http://ant.apache.org/

// Cygwin 1.7 : http://www.cygwin.com/
- For Windows platforms

// Android 2.3.7 (Gingerbread) x86 Emulator Image Add-on:
- http://software.intel.com/en-us/articles/android-237-gingerbread-x86-emu...

// Installing Android SDK:
- http://developer.android.com/sdk/installing.html

// Android Platform Tools:
- http://developer.android.com/guide/developing/tools/index.html

// Installing ADT Plugin
http://developer.android.com/sdk/installing/installing-adt.html

ADT Plugin
[embed]http://dl.google.com/android/ADT-20.0.0.zip

Download the ADT Plugin
https://dl-ssl.google.com/android/eclipse/

// Run on the Emulator
http://developer.android.com/training/basics/firstapp/running-app.html

// Android NDK
http://developer.android.com/tools/sdk/ndk/index.html

// Android* 4.0.4 (Ice Cream Sandwich) x86 Emulator System Image
- http://software.intel.com/en-us/articles/android-ice-cream-sandwich-x86-...

// Android* 2.3.7 (Gingerbread) x86 Emulator Image Add-on
- http://software.intel.com/en-us/articles/android-237-gingerbread-x86-emu...
...

Please take into account that only a couple of first downloads need to be installed. Then, as soon as Android SDK is installed all the rest installations or updates usually done with Android SDK Manager ( very good and simple tool! ).

Hello,

you can also try to develop your applications using the Cross-platform: You write once with Javascript and you deploy it on the other different platforms (Android, Balckberry, iOS...) 

You can start with http://www.dragonfiresdk.com/

or http://developer.android.com

there is PhoneGap which supports all platforms , which also is based on web technologies.
http://www.phonegap.com/