OpenOffice.org uses an XML file format as the default 
for saving and opening its documents.

XML file format names OpenOffice.org uses the 
following XML formats, HOWEVER, in the interest 
of interoperability, it's better to use HTML, 
TXT or use the Microsoft extensions/formats so that PC and
Mac users without OpenOffice are able to open the files.  

Kind of like the idea behind Samba... the Open Source,
Linux and UNIX folks have the power and flexibility
to work with the proprietary nonsense that the Redmondians
perpetuate.  No point in making our files unreadable by
the clueless masses.

Application	          OO extension    preferred extensions/formats
---------------------------------------------------------------------
OpenOffice.org Writer		 *.sxw	  *.doc, *.txt or *.html 
OpenOffice.org Writer templates  *.stw
OpenOffice.org Calc 		 *.sxc    *.xls
OpenOffice.org Calc templates    *.stc 
OpenOffice.org Impress           *.sxi    *.ppt
OpenOffice.org Impress templates *.sti
OpenOffice.org Draw 		 *.sxd    
OpenOffice.org Draw templates    *.std
OpenOffice.org Math              *.sxm
Master documents                 *.sxg