Here is a link to the latest report.
The 1st chart shows that when the economy was going strong (in '06, '07, and even part of '08) average weekly US rail car loads seem to hover around ~325,000 +/- 10,000. During this recession it bottomed out in May at approximately 245,000. It has been higher since that month with the latest (September) average weekly rail car loads at just over 276,000. So things have improved but are no where near back to the run rate we had before the financial crisis.
From the report:
Average weekly carloads on U.S. railroads in September 2009 (276,137) were 2,900 less than in August 2009. All or most of that decline can probably be attributed to severe flooding in the Southeast which shut down some rail lines for a period in September.
Average weekly US rail intermodal traffic (accounted for separately from the numbers above) has also been improving since May.
The average weekly intermodal count on U.S. railroads in September 2009 was 198,647 trailers and containers, up 2,600 units from August 2009 and the highest since November 2008. The last three weeks of September were the three highest-volume intermodal weeks of 2009 for U.S. freight railroads.
I've included the AAR Rail Time Indicators in the links section. The page has both monthly and weekly reports on it.