Hey, over here! I may not be the main content section, but I'm equally as important. Sidebars are perfect locations to include contact information, hours of operation, or navigational links. Put important information here that you want your visitors to see, but not necessarily focus on.
Although your footer is usually under the fold, you can put some useful information and add-ons in here. Try putting your page copyright to mark your territory on your intellectual property, contact information, and maybe even a page visitor counter all in the footer.