Just you need to edit CSS You can get it at hackosphere.blogspot.com/3006/09/3-column-templates-for-blogger-beta_01.html or beautifulbeta.blogspot.com/2006/10/adding-second-sidebar-to-your-blog-part.html You can get many more hacks there Enjoy blogger blogging
You dont ned to edit anything.There is ready to use templates at net.Just searched alot. Google it by "three coulom blogger templates"or three coulom blogger xml templates" or i had used some of them.it is really good page http://www.blogcrowds.com/resources/blogger_template.php/3_column or here: http://tips-for-new-bloggers.blogspot.com/2007/02/three-columns-blogger-template.html or here: http://webtalks.blogspot.com/2007/04/downlaod-three-column-new-blogger.html or whatever ...
You do not need to edit them. You can get a list of some cool templates for blogger at http://toplisting.blogspot.com/2007/07/blogger-templates-of-my-choice.html
I want to make my blog post body and 2 side bars attach to each other.. does anyone know how to do that?