Damon Cortesi wrote a cool perl script that sucks down a user's tweets from 2007 and creates pretty charts via a Numbers.app template on Mac OS X. If you need to, you can use this tutorial that tells you exactly what you need to do to make it work. My use of twitter has been relatively consistent since I started using it back in March of 2007. For some reason, the script reports activity in January, even though I can't see any by going "older" via the Twitter webpage. It looks like I also use twitter consistently throughout the week. The "tweets per hour" chart isn't very useful in my case since my time zone changes on almost a weekly basis.
If you're interested, you can see my entire chart below the fold.
I can't figure out the difference between "top @replies" and "top conversational @s." In my case, they are the same.