In case you have just installed IBM Notes 9 Social Addition and missing the Activities sidebar now: The sidebar is no longer part of the Notes install kit but part of the Connections plugins for Notes. Please check this article
Hide “Activities” sidebar during installation of Lotus Notes client
If you want to hide the IBM Connections “Activity” sidebar as you install a Lotus Notes client you need to add the following parameter to the PLUGIN_CUSTOMIZATION.INI file of the client package: com.ibm.rcp.ui/HIDE_PANEL_com.ibm.workplace.ae.client.views.AESideShelfView=true I did not find that documented somewhere and