how to add buttons on home page in crm 2011

for this:
first : http://gtcrm.wordpress.com/2011/08/24/adding-a-new-button-group-to-the-crm-ribbon/
first go for the SDK :sdk\resources\exportedribbonxml
here you will get the .xml for every enity.
from there we will get the location of the entity.
<CustomActions>
            <CustomAction Id="Mscrm.HomepageGrid.new_cooldrink.CustomGroup.CustomAction"
                          Location="Mscrm.HomepageGrid.new_cooldrink.MainTab.Groups._children"
                          Sequence="110">
              <CommandUIDefinition>
                <Group Id="Mscrm.HomepageGrid.new_cooldrink.CustomGroup.Group"
                        Command= "Mscrm.HomepageGrid.new_cooldrink.CustomGroup.Command"
                      
                        Title="custom groups"
                        Sequence="51"
                        Template="Mscrm.Templates.Flexible2">
                  <Controls Id="Mscrm.HomepageGrid.new_cooldrink.CustomGroup.Controls">
                    <Button Id="Mscrm.HomepageGrid.new_cooldrink.CustomGroup.Button.A"
                            Command="Mscrm.HomepageGrid.new_cooldrink.CustomGroup.Button.A.Command"
                            Sequence="100"
                            LabelText="Connect to linkedIn"
                            ToolTipTitle="TipTitle"
                            ToolTipDescription="TipDescription"
                            TemplateAlias="o1"
                            Image16by16="/_imgs/ribbon/newchart16.png"
                            Image32by32="/_imgs/ribbon/newchart32.png"  />
                    <Button Id="Mscrm.HomepageGrid.new_cooldrink.CustomGroup.Button.B"
                            Command="Mscrm.HomepageGrid.new_cooldrink.CustomGroup.Button.B.Command"
                            Sequence="120"
                            LabelText="Import Company Details"
                            ToolTipTitle="TipTitle"
                            ToolTipDescription="TipDescription"
                            TemplateAlias="o1"
                            Image16by16="/_imgs/ribbon/CustomEntity_16.png"
                            Image32by32="/_imgs/ribbon/CustomEntity_32.png"   />

                    <Button Id="Mscrm.HomepageGrid.new_cooldrink.CustomGroup.Button.C"
                            Command="Mscrm.HomepageGrid.new_cooldrink.CustomGroup.Button.C.Command"
                            Sequence="130"
                            LabelText="Import Contact Details"
                            ToolTipTitle="TipTitle"
                            ToolTipDescription="TipDescription"
                            TemplateAlias="o1"
                            Image16by16="/_imgs/ribbon/CustomEntity_16.png"
                            Image32by32="/_imgs/ribbon/CustomEntity_32.png"   />
                   
                  </Controls>
                </Group>
              </CommandUIDefinition>
            </CustomAction>
            <CustomAction Id="Mscrm.HomepageGrid.new_cooldrink.CustomGroup.MaxSize.CustomAction"
                          Location="Mscrm.HomepageGrid.new_cooldrink.MainTab.Scaling._children"
                          Sequence="120">
              <CommandUIDefinition>
                <MaxSize  Id="Mscrm.HomepageGrid.new_cooldrink.CustomGroup.MaxSize"
                          GroupId="Mscrm.HomepageGrid.new_cooldrink.CustomGroup.Group"
                          Sequence="21"
                          Size="LargeLarge" />
              </CommandUIDefinition>
            </CustomAction>
            <CustomAction Id="Mscrm.HomepageGrid.new_cooldrink.CustomGroup.Popup.CustomAction"
                          Location="Mscrm.HomepageGrid.new_cooldrink.MainTab.Scaling._children"
                          Sequence="140">
              <CommandUIDefinition>
                <Scale    Id="Mscrm.HomepageGrid.new_cooldrink.CustomGroup.Popup.1"
                          GroupId="Mscrm.HomepageGrid.new_cooldrink.CustomGroup.Group"
                          Sequence="87"
                          Size="Popup" />
              </CommandUIDefinition>
            </CustomAction>
          </CustomActions>

In Command Definition:

<CommandDefinitions>
            <CommandDefinition Id="Mscrm.HomepageGrid.new_cooldrink.CustomGroup.Button.A.Command">
              <EnableRules />
              <DisplayRules />
              <Actions>
                <Url Address="http://www.google.com" />
              </Actions>
            </CommandDefinition>
            <CommandDefinition Id="Mscrm.HomepageGrid.new_cooldrink.CustomGroup.Button.B.Command">
              <EnableRules />
              <DisplayRules />
              <Actions>
                <Url Address="http://www.google.com" />
              </Actions>
            </CommandDefinition>
            <CommandDefinition Id="Mscrm.HomepageGrid.new_cooldrink.CustomGroup.Button.C.Command">
              <EnableRules />
              <DisplayRules />
              <Actions>
                <Url Address="http://www.google.com" />
              </Actions>
            </CommandDefinition>
            <CommandDefinition Id="Mscrm.HomepageGrid.new_cooldrink.CustomGroup.Command">
              <EnableRules>
                <!--<EnableRule Id="Mscrm.ConvertActivity" />-->
              </EnableRules>
              <DisplayRules>
                <!--<DisplayRule Id="Mscrm.ConvertActivity" />-->
              </DisplayRules>
              <Actions />
            </CommandDefinition>
          </CommandDefinitions>

Change your entity accordingly.