I had John Hamel do a nice animated GIF advertising banner for me a few days ago, with the intention of running the ad on the Sky & Telescope web site. I will probably still do that at some point--but the ad would cost me about $330 for 20,000 impressions--and I wasn't sure how many of those readers would be Losmandy mount owners.
Google has an advertising program called AdWords; the first block of advertising that you see at the top of this blog is an example of it. It uses keyword selection to pick on which sites any particular ad runs. Sometimes keyword selection causes some inappropriate or not very successful advertising selections. If I blog about homosexuality, and use the word "gay," there's a good chance that a gay dating service ad will appear at the top--and for the most part, this isn't exactly the best choice for a place to advertise products for gay people. On the other hand, for those pages that have historical content, AdWords often does a spectacularly good job of picking ads for history books.
Anyway, here's the cool aspect of AdWords: other than paying $5 for a setup charge, the only time I pay for advertising is when someone clicks on the ad to go visit the ScopeRoller website. If thousands of people see my ad--but never click over--it costs me nothing. If someone is sufficiently interested to click over, there's a good chance that this is someone that might be interested in my product.
The pricing is very clever. You can select a priority for placement of your ad by specifying a maximum amount that you are willing to pay per click--from as little to a penny per click, to whatever amount makes sense. As you increase what you will pay per click through, it increases the frequency with which pages that have matching keywords or phrases will display your ad--and it gives you an estimate of the number of customers that will see the ad. I discovered by experimenting a bit that there was no advantage to paying more than $0.20 per click for one set of keywords, and a bit less for another.
You can also set a maximum daily budget--as soon as you have spent $2 for the day on a particular ad campaign (to use a silly example), it stops showing ads. This helps you to avoid someone intentionally clicking tens of thousands of times on your ad but never buying anything, and driving you into bankruptcy.
The keywords and phrases that I am using are all related to the Losmandy and CI-700 mounts, and so they aren't appearing a lot. Yesterday I only had 31 impressions, and none of them clicked through--but it didn't cost me anything, either.