Authors of these documents often include references and links to sites that they have found useful. You may find the information you need at one of these hyperlinked sites rather than in the HOWTO itself. For example, I found Linux Network Drivers, an interesting site for information about Network Interface Card drivers, in the Ethernet HOWTO.
To find HOWTOs, the first place to go is the Linux Documentation Project (LDP). The LDP includes a HOWTO Index Page that I suggest you bookmark in your browser.
These HOWTOs are written by Linux users and are periodically updated by the authors. Many authors provide the latest version at a personal website and a hyperlink to the latter is typically provided in the document. This version may be newer than the one available at the LDP website.
Note also that other HOWTOs are available, the authors of which have not submitted them to the LDP. It is definitely worthwhile trying to find these using an Internet search engine as I describe in a subsequent section.