http://railfax.transmatch.com/
Here is an example of the information available on this web site. This graph shows Total Traffic for 2008-2009 vs. 2007-2008. There are more graphs and tables on the web site showing data by railroad and by commodity.
Now that we are in the 4th quarter, you can see how rapidly carloadings dropped last year and how they have been slowly increasing in the 3rd quarter of this year. Let's hope they continue that trend.
Note: This web site has new tables and graphs every Thursday. So, if I am late or miss a week with this blog posting, you can check for new data on Thursdays.