If you don't want the programming and behind the scenes nature, maybe Wordpress or Typepad to get you up and running quickly without a fuss.
If you don't mind getting your hands dirty with ultra-customizing every facet of your blog without closed-source woes, Joomla or Movable Type. The latter of which I've been using for about 1.5 years now and am absolutely in love with. That's not to say you can't get up and running quickly with these, but the level of customization they offer are top notch and take a little more time and patience. You can get right into their source code and make your own plugins... in my opinion these also have that "professional"-ism attribute as well.
If you don't mind getting your hands dirty with ultra-customizing every facet of your blog without closed-source woes, Joomla or Movable Type. The latter of which I've been using for about 1.5 years now and am absolutely in love with. That's not to say you can't get up and running quickly with these, but the level of customization they offer are top notch and take a little more time and patience. You can get right into their source code and make your own plugins... in my opinion these also have that "professional"-ism attribute as well.