Jimmy Cornel's World Cruising Routes is great, but he only provides the most common sailing routes for cruising yachts (there is precious little on the Atlantic coast of
South America, for example). The Pilot Charts or Ocean Passages of the World (American or British) provide much more detail if you are thinking about taking routes less travelled or want details of specific areas on more common routes. These are amazing resources for planning your routes, providing
wind speed and direction, currents, sea state,
weather etc. for every month of the year, based on data collected over centuries.