Forum Moderators: open
1 OVerture
2 Google
3 FIndwhat
4 Ah-ha
5. Sprinks and Kanoodle.
I'd say Overture UK and DE are more or less neck and neck with Espotting as of this moment...
Espotting also has France live (and Spain just opened). While Overture hasn't quite launched France yet..
However, if your target market is outside the USA then give Google a try. Google is excellent for geographic targetting - say, for example, if you wanted to hit certain countries and ignore others. For this reason it is my personal favourite.
FindWhat is not a bad third place and a relatively inexpensive way of mopping up the sites that Overture doesn't cover. They even have exclusive on one or two higher profile sites.
I have yet to chew through more than a couple of dollars of Kanoodle credit. If you are selling a product that everyone wants and you can't keep up with the competition on Overture then Kanoodle might be for you. If you have a niche product or a specialised market then forget it. On the plus side they do seem to have extremely good fraud protection to stop you being billed for duplicate click-throughs.
You can get bulk rate deals where you can sign up for several dozen junior PPC sites in one go and get hundreds of dollars worth of free credits. I would tend to be wary of these. Once you get outside the top few PPC engines you are looking at a lot of companies chasing the bottom end of the market - they tend to be a lot less selective about who they take on as customers and affiliates.
Remember, online advertising is not just about clicks - it is also about brand building - so think carefully about who you would like your customers to be associated with in the minds of prospective buyers.