This:
http://www.zamzar.com/ can allegedly convert office file formats online.
Not saying this is any safer than letting one of us resident geeks do it for you, but I guess it is more anonymous by virtue of being online and presumably automated.
Interesting concept though.
Edit: this actually worked - I got the results back about 10 minutes later. I didn't try a spreadsheet with formulas (I will now..I'm intrigued), but it definitely worked.