I just upgraded from CS 2.0 to 2.1.  One of the great new features is the Tag Cloud feature.  Basically you can attach key words to blogs and forum posts, and then visitors can click on those key words in the tag clouds to find related content.

Here's the forum thread on how to install a tag cloud.

Here's what I got from that thread and I'm going to clarify a little:

First, here's the code to copy into your clipboard:

<div class="CommonSidebarArea">
     <h4 class="CommonSidebarHeader">
          <cs:ResourceControl ResourceName="PopularTags" runat="server" />
     </h4>
      <div class="CommonSidebarContent">
           <CS:TagCloud ApplicationType="weblog"           
TagCloudCssClasses="CommonTag6,CommonTag5,CommonTag4,CommonTag3,CommonTag2,CommonTag1" runat="server" id="TagCloud" MaximumNumberOfTags="25" ShowTagCounts="false" IgnoreFilterTags="true" CssClass="CommonSidebarTagCloud" />
      </div>
      <div class="CommonSidebarFooter">
           <a href="<%=SiteUrls.Instance().TagsHome %>"><cs:ResourceControl ResourceName="ViewAllTags" runat="server" /></a>
      </div>
</div>

Second, open the ASP.NET Master page for the Theme you are using.  I'm assuming you are using the default theme, so the file you want is \themes\default\Masters\Master.ascx

Third, paste in the code for the cloud.  I decided to put it here, underneath the standard controls that appear on the right hand side.  Search for this line and insert the tag cloud code directly below:

<td valign="top" id="CommonRightColumn">
            <CS:MPRegion id="rcr" runat="server" />
            [[ OK insert tag cloud here ]]

 Fourth, add align="center".  I added a align="center" attribute to the right hand column cell header tag, so it looks like this: <td valign="top" align="center" id="CommonRightColumn">.  I found that if I didn't have that then the tag cloud would appear offset to the left and didn't line up with the other panels.  Adding this attribute didn't move the other panel items at all.

I'd actually prefer to put the tag cloud inside the controls that appear on the right hand side but I haven't figure out yet which file I need to modify.  I'd like to get it above the Recent Additions panel.  If you know which control it is please let me know.