American Express has a great layout for the Investor Relations section on their website. Check it out here.
The website is split up into comprehensible sections, with links for further information under each category. All information is public, so any financial report can easily be downloaded.
All SEC filings are available online, including the most recent 10K filing for the period ending September 30, 2010 (filed on November 3). A press release was issued to sum up the quarterly report, stating that the net income has increased 71% since last year ($640 million in 2009, $1.1 billion currently).
Additionally, losses totaled have also decreased, which the company believes is a sign of continuing credit improvement.
The press release is also available online for investors to review.