The Web is full of directories and groups that try to make sense of all the sites you can visit. Some are manually created directories, such as those from Yahoo! and Google (Figure 16-1). One of the easiest ways to ensure you’re aware of your competitors is to find yourself in a directory and see who else is listed there.

Figure 16-1. Car rental companies in Google Directory

But directories are built by fallible humans, and sometimes your competitors won’t be included. You should search for specific terms and see what sites come up, and use Google Sets (http://labs.google.com/sets) to enter your known competitors and see if there are others you don’t yet know of.

Once you’ve got a list of competitors, it’s time to determine who’s a threat.