The Filewizard website is pretty bare-bones, and so far it appears to deal with software for PCs (though some of the file types discussed are from the Mac world), but if you need to create or open a compressed file of a particular type, it’s worth checking here.
Yesterday I mentioned the fact that archives (and backups too, actually) are often compressed so that they take up less storage space. Nathan Cser has a website dedicated to compressing and extracting files. Set out in table format, the Compression Guide and Extraction Guide show you which types of compressed files you can create/open with what program. Below the tables are links where you can download the programs, many of which are freeware or shareware. His favorite seems to be the freeware program ZipGenius, by the Italian software company of the same name. (It comes with both Italian and English interfaces.)