This isn't really that important, but is there a way to change the Geany IDE's sidebar to the right side instead of the left?
The answer is yes, but it depends on which version of Geany you are using. Check out this mailing list entry and read through the discussion.
The change was committed in October 2009. Which according to the homepage means it is in version "Geany 0.18.1".
You can get this version from here.
I personally am using 0.18, released in August 2009, so have not tested this works.
EDIT: Following the comment, I have checked the source and can confirm the code does not appear to be there to alow this functionality.
The answer therefore is you should be able to, but you cannot.
I asked on #geany on freenode.net about this missing functionality, but have not had a reply yet.
You may get a result if you report this as a bug.