As of 2015, a good location to find metric fastener charts is the Engineers Edge website. This site contains a variety of ISO metric hardware specifications.
The Engineers Edge site provides charts for various fastener sizes. Some sizes available include M9 to M24, M24 to M50, M52 to M72, M75 to M120, M125 to M180 and M183 to M230.
Another good location for finding metric fastener charts is the American Fastener website. It offers charts for fastener standards and guidelines for fasteners, including nuts and bolts.
The Fastener Mart website also provides users with helpful information on the basics of metric sizes and threads.