Xfig has a man page and HTML and PDF versions of its manual. The manual covers the use of every menu option and tool in quite a lot of detail, and resembles a traditional manual. Probably due to its age, it’s quite a wellknown application online, particularly in academic circles.
The Inkscape project has a dedicated documentation team, and the documentation is extensive. In addition to the thorough, traditional manual, along with other useful information, the official site features some tutorial material demonstrating how to carry out some common tasks. Inkscape is quite a popular cross-platform application, and this popularity means that it is well served by YouTube tutorials. The official website forum has good activity levels.