In order to advertise in Google search engine and their partner network you need to signup with adwords and advertise there , in the same way if you are looking for advertising on Yahoo.com search , and their partner network then you need to signup for yahoo sponsered search and get started for free using this special 125$ Coupon.
You can try out promoting the best affiliate programs available on the internet or start promoting the products you found via commission junction and all these things for FREE! Yahoo has recently started a new coupon which offers 125$ once you signup and start advertising after verifying your account. Once the free credit is completed you can add your credit card and continue your advertising promoting your own websites or affiliate programs.
I would suggest you to signup now , complete the registration and start promoting the web hosting companies using this free coupon with a 25 cents/click advertising costs which means you get a minimum of 500 targetted visitors and start promoting the web hosting affiliates, where in if you expect a minimum of 2% signup’s you can get around 500 X 2% = 10 Web hosting clients which can pay you a minimum of 1000$ commissions via commission junction.
There are many other affiliate programs which pay depending on the niche you select and pay from 50$ to 300$ per sale, so try to monetise this 100% free coupon and make a minimum of 1000$ from it. Let me know if you find any problem signing up this coupon.