do you want to a tag cloud like the one in my blog ? it easy
1- add a gadget and select html/java script to your blogger
2- copy and past this code

<div id="w2bFlashContent"><p style="display:none;">Flash Labels by <a href="http://www.way2blogging.org/">Way2Blogging</a></p></div>
<script type="text/javascript">
/*<![CDATA[*/
var w2bFlashLabelSettings = {
    blogurl        : "http://heaven-downloads.blogspot.com",
    color          : "FFFFFF",
    hoverColor     : "333333",
    backgroundColor: "FFFFFF",
    size           : 12,
    speed          : 100,
    width          : 250,
    height         : 300,
    transparency   : true
};
/*]]>*/
</script>
<script type="text/javascript" src="http://widgets.way2blogging.org/blogger-widgets/w2b-new-flash-label-cloud.js"></script>

3- change the URL with red to your blog URL
4- you can change the colors , by replacing the codes ( color , hoverColor , backgroundColor )
5- save your gadget
NOTICE: you should add a labels gadget to your blog so the tag cloud will work