I have noticed that there is some really really cheap traffic and link popularity to be purchased on blog websites.
Some sites get tons of pageviews, and some have tons of link popularity. Some blogs have both and prices that do not cost the farm.
If you look through an article about the most famous blogs in the world you can see just how cheap this ad space is selling.
The first blog is a lawyer blog and the second site listed is the New York Times, but if you scroll past them you can see some pretty cheap ads.
Gawker is one of the most famous blogs on the web (and it costs $400 / month or $150 / week). I am probably not going to be advertising on the Gawker website today, but currently someone is with a Texas Holdem website.
I am sure that link is probably cheap for someone in the gaming industry. Those affiliate checks online casinos send you can get fat. I had one page from when I first started learning about the web that got me a few grand without me actively promoting it...
If you used the right political message or were marketing an amazing idea the cheap entry price of advertising on Gawker could easily pay for itself tenfold.
Once you look at some of the slightly less popular blogs the price drops sharply. Advertising on one of the top NanoBot site is $60 / month.
Some second and third tier blogs are priced dirt cheap. I think the two biggest players in the blog ad arena are:
http://www.marketbanker.com/mb/
http://www.blogads.com/
There are also some smaller players too, such as
http://www.textads.biz/
I may soon promote a stupid idea I just came up with :) More on that later...I thinking...