Of the top three Open Source Content Management Systems, I've adopted Drupal by Dries Buytaert. It's technically richer, more logical and extensible than Joomla imo. From what I've read Wordpress is easier to craft, but I haven't personally worked with it.

My sites are served by an Ubuntu Debian LAMP on an Intel P4 Intel Mac Mini with 5/30 Mb cable broadband. A little Gig-E here, a little powerline ethernet there, et voilà, up the router.

Using a KillaWatt, I measured the idle power consumption to be 120W 30 Watts. So at my utility rate of ~.11c KWh that's about $2.29 per month, or less than $30 smackers a year. Much more cost effective than dedicated hosting, much more versatile, and hella more fun.