Have you ever noticed how you get that weird link in your referral log? Have you ever wondered how someone searching for that bizarre keyword found your site?
Welcome to internet viral marketing. That activity that promotes everyones favorite sites, comics, cartoons, movies and whatever else without you paying for it.
It used to be that the only way people found your site was through search engine "keywords" that you put in your webpages, then the search engine accelerators came along and clogged everything up. Along came Google, where it was now a free for all, whatever you linked to and everyone else linked to was now the top result for that word.
One person on the french toast forum plugs their favorite comic, YOUR comic, and nearly everyone who reads that forum thread will get their curiosity perked. People who are part of a community tend to trust others in the community.So when you start seeing referrers from that french toast community, and can't figure out why they'd like your comic, maybe you should drop in and say thanks, that may encourage others to come back.
Chatrooms and IRC are another source of silent viral marketing, but are just as important as the odd forum plugging your comic. People in IRC/chatrooms tend to rapidly topic switch, so anyone who posts something there, has a 5 minute window of opportunity to visit your site, and then the next fun link will come up.So what do these have in common? People tend to be members of multiple communities, and one cool thing will be spread to other communities with ease.
There are still some unexplored print-comic/web-comic/flash cartoon centric viral marketing though. Developing a sample/teaser that can be dropped into the P2P networks, and getting multiple people to seed it wil bring it's visibility up on the P2P networks, water-marking your images with your site address will help people find your site.
Video blogs haven't really picked up on webcomics yet, since most video transmission doesn't have an active way to visit a site mentioned in it, however look at video blogs as the next piece of viral marketing. Make some 30 second flash teasers and get them onto the video publishing sites.
All of this happens without any cost to you, but nobody said you can't initiate it. Put your webcomic link as the only link in your sig, with a small banner if possible. Contribute to various communities. Some will be more receptive than others, but finding that one community that loves what you do can be rewarding.
Your fans are your best form of stealth viral marketing. Interact with your fans, the ones that will stay and defend you to the death on other communities are the ones that feel they are the closest to the author/writer/artist/etc, even if they are not. Sometimes it only takes one response from you for that to happen, they will then feel they are closer to you than everyone else who hasn't received a response. Meeting fans in person though… that may earn your some life long fans, and some stalkers.
So in short, without investing any of your own money it is possible to grow your reader base just by being part of a community, any community. One friend tells two friends who tells two friends, etc.
Maybe you can be the next snakes on a plane.