Expriences with Open Source Web Technologies?

_ZorKa_ asks: "I have been asked to give a presentation at an up and coming technology expo by my employer about 'Open Source Web Technologies'. Having taught Linux courses and open source web languages at a local college I feel fairly comfortable in speaking on the subject in front of a large crowd. So, instead of giving some of the same old boring open source stories I normally use I thought I would poll the Slashdot audience and see if there is anything of particular interest I should mention during my presentation. Maybe you have a war story to tell, or some advice to give. Anyone have any great stories that I could pass on as to why you *should* use open source web technologies in a business? Anyone have any links to some sound numbers that can back an argument up with. Even if you have reasons why a business shouldn't use open source web technologies I would like to consider those as well. I'm all ears!"