Do you have a file that you can't read (such as a postscript file) because you don't have an application that knows how read it? Sometimes your only solution is to convert it to another file format (such as a Adobe Acrobat document).
Zamzar is a free web site that supports conversion of files between a wide variety of different formats (i.e.: document, image, music, and video). The site is adding support for new formats whenever they can.