Add a Button to the Ribbon

Scenario:
To add a button to the sharepoint 2010 ribbon interface, is pretty much the same as adding Custom Action in MOSS 2007.

Solution:
Here's the element manifest file for developing a feature for adding a button to the ribbon to the Library tab in the Actions group for a document library (Type=101).

Element Manifest for the Feature:

<?xml version="1.0" encoding="utf-8"?>
<Elements xmlns="http://schemas.microsoft.com/sharepoint/">
      <CustomAction Id="Ribbon.Library.Actions.AddAButton"
                            Location="ViewToolbar"
                            RegistrationId="101"
                            RegistrationType="List"
                            Title="Add a Ribbon Button">
                 <CommandUIExtension>
                      <CommandUIDefinitions>
                                     <CommandUIDefinition
                                      Location="Ribbon.Library.Actions.Controls._children">
                                             <Button Id="Ribbon.Library.Actions.NewRibbonButton"
                                                     Command="NewRibbonButtonCommand"
                                                      Image16by16="/_layouts/images/FILMSTRP.GIF"
                                                      Image32by32="/_layouts/images/PPEOPLE.GIF"
                                                      LabelText="New Button"
                                                      TemplateAlias="o2" />
                                     </CommandUIDefinition>
                     </CommandUIDefinitions>
                     <CommandUIHandlers>
                         <CommandUIHandler
                             Command="NewRibbonButtonCommand"
                             CommandScript="javascript:alert('This is a new button!');" />
                      </CommandUIHandlers>
                    </CommandUIExtension>
         </CustomAction>
</Elements>