The Aldrich site has MSDS sheets for many of their compounds. Links to MSDS sheets will appear on the left hand side of the page, when you are looking at the record for the compound. You may have to click the "MORE" link to see it.
MSDS SheetsThis site claims to be the clearinghouse for MSDS sites on the Internet. Many different kinds of searching allowed, including by manufacturer. Includes links to all important MSDS sites, with search engines for each one.