The best known places to do CPC (cost per click - also called PPC, price per click) advertising are Google and Yahoo Search (formerly Overture). We weren't able to strike a deal with Google, but if you sign up for a Yahoo Search account through the link below, you'll receive a bonus $25 in clicks when you initially deposit $50.
Yahoo! Sponsored Search lists your business on top sites like Yahoo!, MSN, AltaVista and CNN. Sign up and get a $25 credit. 
You can get clicks for 10 cents each through Yahoo Search, that extra $25 translates into 250 free visitors to your web site - not a bad deal.
In addition to the big two, you can also sign up for these CPC search engines as well:
Miva Merchant (deposit $50 and receive a $5 free credit) Sign-up Now
Search 1-2-3 (Deposit $50 and get $20 free) Sign-up Now
Enhance (Sign up and get $25 free) Sign-up Now
So if you sign up for Yahoo Search, Search 1-2-3, Miva Merchant, and Enhance you get a total of $75 of clicks for free. Yahoo is the only one with a 10 cent minimum (the others are 5 cents) so that's a total of 1,250 free visitors (it's a great way to start off your web business).
We weren't able to swing it so you get free clicks with AdSonar, but it's also definitely worth checking out and possibly signing up for.
AdSonarSign-up Now