Each year, members of Congress file 'personal financial disclosures' regarding their various assets and sources of income. In these documents, legislators provide detailed lists of their investments in anything from real estate to mutual funds and company stock.
Find it here. As an example, with the question of Net Neutrality coming up, it is interesting to note that Speaker of the House John Boehner has held up to $50,000 worth of stock in mass media company, Comcast, in a tax-deferred account.
Editor's note: For the richest members of Congress (with Rep. Darrell Issa and a net worth of $357.25 M leading the list) compiled by CQ, go here.