The Factorio Wiki is managed and updated/changed by one of the members of the Factorio development team. It is a good source of information for all major parts of the game!
The official forums have a very large and helpful community that are always willing to help and answer questions. There are also many helpful topics under the Gameplay Help section, with things from helpful tips and builds, to video tutorial links, and even Combinator & Circuit Network guides and explanations.
A very good train tutorial made in a Google Docs Presentation. It covers everything from the locomotive GUI and what everything does, to Train Stop setup, to Signals, as well as creating junctions and more. Definitely something to check out if you are struggling with Trains.
Additional viewing formats can be found here.