How can I put extra banners or ads into my website when I have space on the right and left side???

My question is about a site I own named "http://6dollar-tacticspays.com" I have putted banners and ads into my reseller website, but now I have lots of space on the right and left side. I think now that the site is too long (you have to scroll a lot to see all my banners and ads), so I was hoping that somebody knows more about html codes to fill up that unused space. I hope you all understand whatI mean and hope to get some help with this !!! Thanks and have a sweet 2011 all!!!!