Converting file formats online
There is a handy free online service allowing conversion between number of file formats (including some rare document formats). Many open formats are among supported formats:
Recently I needed to convert MS Publisher file into something else. *.pub files are virtually unconvertible (unsharable) and while I didn’t find any solution that would give me an editable file in open format, ZamZar helped me to at least get hold on Pdf export from proprietary MS Publisher file format.