As a webmaster or content publisher you have an opportinuty to monetize (make money from) your websites 8)
Here is a running list of good advertising opportinities available:
Advertising Networks
Using one of these ad networks is easy and straight forward. Join and get a code snippet to place somewhere in your HTML. Ads are served automatically and you get paid for click-throughs and/or impressions.
Google Adsense (http://adsense.com)
Value Click (http://www.valueclickmedia.com)
VigLink (http://www.viglink.com/?vgref=551397)
InfoLinks (http://www.infolinks.com/join-us/?aid=1437369)
Bing Ads (https://secure.bingads.microsoft.com/)
Chitika (http://www.chitika.com)
Affiliate Networks
Affiliate networks are a little different. With these, you join and then subsequently join specific merchants' programs within. You choose the ad and you typically get paid for actions following click-throughs, for example any sales or leads you generate.
Commission Junction (http://www.cj.com)
LinkShare (http://www.linkshare.com)
Share A Sale (http://www.shareasale.com/r.cfm?b=69&u=62759&m=47&urllink=&afftrack=)
Others
Amazon (https://affiliate-program.amazon.com/gp/associates/join/landing/main.html?tag=dynawebdesign-20)
Do you know of any more? PM me and I will add them to this list.