This is one of the easiest twitter graph tools I've seen. 

1. Go to http://xefer.com/twitter

2. Enter your Twitter Id and hit Get Data

3. Wait for the site to collect the data and generate the graph (and the reply explorer which I didn't capture in the screenshot below).

If you want info on how the data is collected you can check the xefer blog post and discussion. 

The cool thing is that you can see the stats for any public twitter account. So if you are wondering what the tweeting habits of those "social media experts" are, you can plug in their Twitter Id and take a peek.