You will find that if you're excellent at what you do, people will come to you. I get five or six website messages per month from people asking for mice, and I never advertise explicitly (other than in my signature on forums). This is true not only in mouse breeding but in anything, really. Word gets around on the quality of your "product," no matter what you're producing. Even with all the advertising in the world, if your "product" is less-than, it will fail at being desired. This is basic economics. It's weird to think of it applied to mice, but it works the same way.
It never occurred to me to make a poster.
For what it's worth, I wouldn't use Craigslist or freecycle-style sites because of the danger that people can lie. I've heard rumors of people picking up kittens on "free to good home with adoption fee" ads and feeding them to their snakes. Whether that's true or not, the possibility scares me. I know that snakes have to eat, too, but with the years and thousands of dollars we spend on our mice, I can't imagine a potential BIS becoming dinner.
If you have surplus babies, often the most humane thing to do with them is actually to euthanize them, especially considering the treatment mice get in pet stores. Mice are loss leaders, anyway, so there is no real or substantial profit to be had, even on show mice.
Agoutis and PEWs usually produce more agoutis and PEWs (and blacks). These are the most common colors in petstores around the world and are even harder to find pet-homes for than other kinds of mice.
P.S. Your website does not work. Did you mis-type the URL, perhaps?