The following video, from The Open University, illustrates some of the awesome ways bacteria have exerted an incredible influence in the world for as long as we have historical records.
You like your beer, for instance? Next time have a toast for our fellow unicellular organisms because without them, your beer would just be some nasty, bitter juice that tastes like piss :)
Oh, did I mention they also write some awesome romantic poetry? :)
And for more, check out how viruses invade your body. It's scary, but a testament to the blind ingenuity of evolution.