XHTML code to create sidebar within a post?

You could float the stuff you want to separate out by editing it in HTML view. Example:

<div id="linkside">
put your links here
</div>

Then in your stylesheet:

#linkside {
 float: right;
 width: 200px;
 padding: 0 0 10px 10px;
}

Lots more about floats: http://css.maxdesign.com.au/floatutorial/