I've relied heavily on search traffic / SEO, because it provides ongoing benefit even if I step away from it for a while.
It's an easy fit for the information-focused sideprojects I've typically created, providing the content needed to rank with no additional effort, but it can work for any project creator willing to put a little effort into creating content about their project and promoting that content (to gain links to their domain). And most importantly, it keeps me focused on creating something people want, because I'm typically expanding the project in areas where I see there's a high volume of searches (through keyword research tools).
It's an easy fit for the information-focused sideprojects I've typically created, providing the content needed to rank with no additional effort, but it can work for any project creator willing to put a little effort into creating content about their project and promoting that content (to gain links to their domain). And most importantly, it keeps me focused on creating something people want, because I'm typically expanding the project in areas where I see there's a high volume of searches (through keyword research tools).