To answer your question while package names do not have to begin with com, org etc. they typically do. Convention many companies follow is com.companyname.businessunitname.projectname.modulename.whatever You may add or take out stuff from above as needed. If I were writing a test programs, I would simplay create a package named 'test' (without quotes) and it would be perfactly valid.
Download any jar file such as junit, struts, commons logging, log4j and open it with winzip you will see package structure under path column. That should give you a pretty good idea.
If you are writing your own personal application, feel free to give whatever package name you want (make them all lower case by convention though). If I were you, I would put my name in it so if some one decides to download or distribute my code, my name also goes out there
Edit: Forgot to add that if I were HFSJ, I would put com.oreilly.hfsj.chapterx.example or something similar [ August 25, 2005: Message edited by: Chintan Rajyaguru ]