My brother and a very good friend recently launched a little web 2.0 site around ranking webcomics, KungFuGRIP. It rips on the Digg/Reddit model, but specializes in a narrow vertical. The cool thing is it got created and launched with nothing but some time investment:
With the Web of today you can put something up with little heavy lifting. An engineer friend and I built the majority of my last project, KungFuGRIP, in a Sunday afternoon using Drupal. Once live we started making tweaks based on user feedback.