What types of files should I upload as instructional materials?

That depends.

If you have chosen the Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License (CC BY-NC-ND 3.0; http://creativecommons.org/licenses/by-nc-nd/3.0/), then you would probably want to upload a file format that is difficult to manipulate or modify, such as a password protected Acrobat (PDF) file.

On the other hand, if you choose the license that encourages others to modify or improve upon your work as long as they cite your original contribution (Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License (CC BY-NC-SA 3.0); http://creativecommons.org/licenses/by-nc-sa/3.0/ ) , you should upload a file format that will be usable by the greatest number of users and which will stand the test of time. For instance, rather than upload a document in Microsoft Word (.doc, .docx), consider uploading a document as a Rich Text Format (.rtf). Instead of uploading a Stata file (.dta), consider uploading tab-delimited (.txt) or comma-delimited text file (.csv).