ORDER BY specific values

Hi Everyone,
I was wondering if there is anyway to ORDER BY in a query by certain values first. I have a table with Projects and subprojects and sub-subprojects and I always want to display the parent project first. Is there anyway that I can do that.
Thanks for all your help.Could you give us a little inside information about your data-structure, eventually accompanied with some sample data and the way you would like to have it ?sql