EDIT: Link isn't working for some reason! Copy and paste or click link in post below - http://www.zamzar.com
Saw a post the other day about PDFzilla, software for making editable docs from pdfs, which made me think to post this.
I have used a site called Zamzar for many years. You basically upload your doc/pdf/odf/jpeg/png/xls/txt/mp3/wav/avi/wmv/flv etc etc etc and the site offers you a list of possible conversions.
Select what you want, stick your email address in and off it goes. Uploads your file and emails you a link to download the converted copy.
It literally does any type of file, I have used it for converting Youtube videos to avi, created editable pdfs, converting MS Works docs to MS Office formats.
Full list of file types here:http://www.zamzar.com/conversionTypes.php
Superb website and well worth having in your favourites, results are normally bang on. PDFs can be an issue, but I think that is the case for most software, certainly the ones I have used!
Supports file sizes up to 100MB, which is pretty huge, you can pay for file sizes up to 1GB