To add advertisements to Community Server 2008.5 blog posts, do the following:

Add the following:

<%@ Register TagPrefix="CSUserControl" TagName="AdTop" Src="Ad-Top.ascx" %>
<%@ Register TagPrefix="CSUserControl" TagName="AdBottom" Src="Ad-Bottom.ascx" %>

to the top of the posts.aspx file under the Themes directory.

Add the following:

    <CSControl:AdPart runat = "Server" contentname="StandardTop" ContentCssClass="CommonContentPartBorderOff" ContentHoverCssClass="CommonContentPartBorderOn">
    <DefaultContentTemplate>
    <CSUserControl:AdTop runat="server" />
    </DefaultContentTemplate>
    </CSControl:AdPart>

to after "</CSControl:Title>"

Add the following:

        <CSControl:AdPart runat="Server" ContentName="StandardBottom" ContentCssClass="CommonContentPartBorderOff" ContentHoverCssClass="CommonContentPartBorderOn">
          <DefaultContentTemplate>
            <CSUserControl:AdBottom runat="server" />
          </DefaultContentTemplate>
        </CSControl:AdPart>

to before "</asp:Content>", near the end of the file.

This will show ads at the top and bottom of any/all blog post.