Here are a few options you can consider -
Yahoo Search Marketing - Content and search
MSN AdCenter - Content and search
AdBrite - Content network advertising
Ask.com - Content and search
The above options are paid, but all are cheaper than AdWords.
As for free options, you can browse through web hosting forums and generally find directories that will allow you to list your site for free. These won't provide a ton of traffic, but it's a start.