Wikipedia user Leon Weber has created a tool that lists the most-viewed Wikipedia articles. Here's the link for the top 100 articles in English -- use the drop-downs on the right to filter the list to show other languages. You can also filter the number of articles in the list.
Right now, current news headlines are dominating the rankings, with articles about Pluto, Hurricane Katrina and Comair Flight 191 topping the chart. After that, the list descends into the pedestrian and predictable topics of sex, pornography and pop culture stuff like Pokemon and Lost. There are also a few surprises (Doctor Who at #55 and Led Zeppelin at #77).
The tool is a fun and useless measuring stick. Enjoy.