It can be really frustrating trying to get a graphic in the right format for a given application.  Say you need a jpeg or a gif for your web page, but you have a bitmap (bmp).  You're thinking you need a special piece of software, right?  More often than not, no.

Most graphics viewers will allow you to save whatever graphic you are looking at in another format.  Just look under File, then go to Save As.  There is almost always a list of available formats to save it under.
 

Something similar is true also for changing text between formats.  Most word processing programs allow you to save in more primitive formats (e.g., Word format into "ASCII" or "RTF") as well as converting between applications (e.g., Word Perfect to Word).