dasBlog has a TagCloud feature which you can use to replace the Category List that is setup in most of the themes. Here's how I replaced the Categories listing displayed by default in the calmBlue theme with the Tags section you see in the right-hand section of this site.

First, decide if you want to create a new theme or modify the existing theme files. To create new theme, copy the contents of the theme you want to start from to a new directory and then update the theme.manifest file with a name and other meta-info for your new theme.

Next, open base.css and add CSS for the required TagCloud styles (you can modify these to be whatever you like, they just have to be present for the tags to display):

/* TagCloud styles */
.tagCloud 
{    
    LINE-HEIGHT: 200%
} 

A.smallerTag 
{    
    FONT-WEIGHT: normal;    
    FONT-SIZE: 105%
} 

A.mediumTag 
{
    FONT-SIZE: 115%
} 

A.largeTag 
{
    FONT-SIZE: 120%
} 

A.smallTag 
{
    FONT-SIZE: 110%
} 

A.smallestTag 
{
    FONT-WEIGHT: normal;    
    FONT-SIZE: 100%
} 

A.largerTag 
{
    FONT-SIZE: 130%
} 

A.largestTag 
{
    FONT-SIZE: 135%
}
/* end TagCloud styles */      

Finally, open the theme homeTemplate.blogtemplate file and modify the section that is currently displaying the Category listing to display a TagCloud instead. Here's how it looks in my theme after modifying the calmBlue theme:

<table class="MarginSection" width="100%" border="0" cellpadding="0" cellspacing="0">
    <tr><td class="MarginSectionHeading">Tags</td></tr>
    <tr><td class="MarginSectionBody">
        <%drawTagCloud()%>
    </td></tr>
</table>

If you would like a closer look at the code, here's a zip file (3.13 KB) of the work-in-progress theme as of 12/30/08.