CSGNetwork.com provides a metric chart for machine screw sizes and EngineersEdge.com offers a list of links to metric size charts for various types of screw and fastener sizes. In addition to a drill screw metric size chart, CSGNetwork.com offers a tap and clearance drill screw size chart.
A drill size conversion table and a tap drill size calculator are also featured on CSGNetwork.com. EngineersEdge.com offers links to metric size charts for Phillips, slotted and hex head screws. The links lead to charts provided by ISO Metric Hardware Specifications. Some of the specifications on EngineersEdge.com are not guaranteed to be accurate, as of 2015.