This.
Also,
http://www.gunnerkrigg.com is good for one with a plot and great design.
http://drmcninja.com is over the top with a ninja who's also a medical doctor. Much fun ensues.
http://www.wetherobots.com is a really good, lighthearted funny one.
http://wondermark.com does one-off strips of pure absurdism.
http://www.uglyhill.com/ is another great plot-based one.