You can also purchase mailing lists at a reasonable price, and can set criteria for what sort of person appears on your list. Mail advertising annoys people, but they do pay closer attention to it than they usually would. With direct mail, someone has to physically pick up your advertisement, read it, and throw it away if they don't want it. It might cost you 30-40 cents for each piece of mail sent, but every person will read your name. It's up to you to decide whether that's worth it.
Bumper stickers are a great, inexpensive way to advertise.
They are fairly easy to design yourself provided you have the right software, plus they aren't too expensive to print. Print up about a thousand bumper stickers and distribute them freely to friends, neighbors, coworkers, family members. Every person that uses your bumper sticker will be plugging you every time they get behind the wheel. T-shirts are another good example. If you have a nice shirt design, it will be noticed every time you or someone else wears it.