This post (How to exclude holidays in sprint planning as saturday & Sunday so it does not show in burn down charts ) shows how one can hide periodic non-workdays from the iteration burndown chart? Can other special non-workdays such as occasional holidays can also be specified so that they don't show up in the burndown chart?
You can't exclude holidays but you can exclude Saturdays and Sundays if those are not normal workdays for you.
To do this you can go to the workspace settings using the hammer and wrench icon (Provided you have the correct permission levels) and selecting the workspace in question
Under the actions option in the upper right hand corner select Edit Workspace and you will see the following settings.
You can select the workdays you want to included.
Please let me know if you have any questions.