What's new in Android 5.0 

• Android 5.0 brings Material design to Android and gives you an expanded UI toolkit for integrating the new design patterns easily in your apps.
• New 3D views.
• Built-in activity transitions. 
• Android now runs exclusively on the new ART runtime.
• Heads-up notification
• Advanced connectivity
• High-performance graphics
• New types of sensors.
• Read more about it here.

Must Read : Updates about new APIs...

See the Changes from API 20 - API 21


Below are links for downloading the developer tools API level 21, offline, alternatively you can download from your SDK Manager.

Installation

Copy downloaded *.zip(s) in temp folder    ~/../android-sdk/temp/*.zip  

Open SDK Manager >> Check Downloaded SDK(s) >> Click Install.

Download Developer Tools, API - 21

SDK Platform API - 21 (Android SDK Platform 5.0)

      Android-21_r01.zip 


ARM EABI v7a System Image, API - 21
 

      Armv7a-21_r01.zip  


Intel x86 Atom System Image, API - 21


      Intel_x86_atom_r01.zip  


Intel x86 Atom_64 System Image, API - 21


      Intel_x86_atom_64_r01.zip  



Google API for Maps, API - 21


      Google_apis-21_r01.zip  



ARM EABI v7a Google API(for Maps), API - 21


     Google_APIs_ARM_EABI_v7a_r02.zip  



Intel x86 Atom Google API(for Maps), API - 21


     Google_APIs_Intel_x86_Atom_r02.zip  


Intel x86 Atom_64 Google API(for Maps), API - 21


     Google_APIs_Intel_x86_Atom_64_r02.zip  


Samples for SDK - 21

     Samples-21_r03.zip


Sources for Android SDK, API - 21


      Sources-21_r01.zip 


Android TV ARM EABI v7a System Image, API - 21


      Android_tv_armv7a-21_r01.zip  


Android TV Intel x86 Atom System Image, API - 21


      Android_tv_Intel_x86_atom_r01.zip  


Docs for Android SDK API - 21
 (replace the docs folder, but, this will be of no use, please refer online)



 ~\..\android-sdk-windows\docs\ (Unzip files)
      docs-21_r01.zip