Now that we've looked at a few of the major Open Source programs I thought I'd give a little summary. Here is why I like open source...

It's free
    And not just free as in cost, but also free to change. Anyone (who knows how) can look at a programs source and make sure it's not doing anything annoying or stupid.
It can be very good
  Some (Firefox) are much better than the closed source version. Some (Open Office) are good enough to be a viable alternative. Others (Linux) can be a matter of preference.
It makes me feel good
    Having a computer and good software can help kids in school, help people get good jobs and in general help in life.  Anything that can lessen the gap between the rich and the poor is a good thing in my book.

Check out this site for a list of good open source programs that covers most everything you do on a computer.

If you are on a mac, try this list.