You want to find a baby sitter. You'd like to sell your old DVDs. You're starting a home gardening service. There are many reasons for placing an ad, and if you can do it for free you'll be ahead of the game. Instead of paying for small town newspaper ads, put your notice where people will see it every day, and don't pay a penny to do it. Use a mixture of the tried-and-true and the high-tech, and you'll have a better chance of getting results.
Craigslist is one of the most popular advertising sites online, and the ads are free to post. There are different editions of Craigslist for many areas of the country; most large cities have their own version. Go to craigslist.com to see your local site and investigate the wide variety of advertising available at no cost to you. You will find sales ads, job listings, wanted pages and more.
If you have something worthwhile but you just don't need it around your house any longer, advertise it on freecycle.org. There are hundreds of local freecycle sites, and it only take a minute to register. You can post ads for items that you want to give away for free, or put up an ad if you want someone else to give you something that you need.
Most grocery stores and supermarkets have a bulletin board in their entrance lobby. These boards are the perfect place for extremely local marketing. If you have a need for a baby sitter in your neighborhood or want someone to take away a cut-up tree, post an ad on the local bulletin board. You're just about guaranteed that only your neighbors will see your ad and respond.
Facebook and Twitter
If you're looking for something more universal with your ad, post it on Facebook or Twitter. Put a link to your site in the ad so that people can easily click over to investigate your work. This method works well with advertising websites and calls for action such as flash mobs and protests.