In Blogger Beta you can move the widgets up and down, but you can’t flip the post body to the right or left of the sidebar. Here’s an easy way to do that without widgets.
To move the sidebar to the left find the section main or main-wrapper and change float:left to float:right, then find the section sidebar or sidebar-wrapper and change float:right to float:left. To move the sidebar to the right just do the opposite, change float:right to float:left and float:left to float:right.
After flipping them you might want to flip the backgrounds as well, and fine tune the layouts to make your blog look well.
Here’s the picture of the template TicTac Blue with the sidebar on the left: