According to an article in The New York Times today, Barack Obama's inauguration ranked as the 5th highest traffic generator on the Internet as measured by Akamai since they started tracking this sort of stuff in 2005.

The top events in case you don't follow the jump are:

5. Barack Obama inauguration

4. 2006 College basketball playoffs day 1

3. 2008 College basketball playoffs day 1

2. US eliminated by Ghana in 2006 World Cup

and the #1 traffic generating event according to Akamai....

1. 2008 US presidential election

Today's inauguration event displaced day one of the 2007 US College basketball playoffs to capture the #5 spot.

Events are measured in terms of peak visitors per minute to Akamai's system.  It would be interesting to see what bandwidth consumption is like and number of concurrent connections to gauge how things like video streaming are altering traffic patterns.