Dan,
Google is all I have used because I am still amazed about the control one has on AdSense and AdWords and the analytics is very helpful. Reminds me I need to improve my Froogle activity.
Bottom line is you need to decide what culture you want on your site. Paid subscriptions need to provide value and support and the free site can't be littered with flashing ads all over the place. While adding value, you deserve to earn money for the value and traffic you drive - consider income from advertising even if you decide to have a paid subscription site. I do both. This forum as an example, has a paid member site as well as an open forum. The open forum generates revenue paying for all my online activity now -- took about a year..I know people who are making a living online via AdSense.
Here is a cool story - A great company in Denver called
Brand Iron uses AdWords and I had someone notice their ad on the YouTube video blog you will see on
PersonalBoardofAdvisors.com . We talked about it, I happen to know the founder and who knows, win:win:win? Relevant placement:click:meeting
If you are driving traffic to a focused topic, I would use Google products, Dan. I hope this helps.