There are two main ways you can make money with search engines. You can either join a PCC website and get a very small percentage of money per click or you can park your domains on a domain parking website. Both of these work about the same way. With a PCC site you will receive an affiliate search engine where you can send traffic, when people do searches on the site, or click keywords on the site you will receive a small amount of money per click. Once you reach a minimum amount of money you will get paid. Now this way is for the little guys. I wouldn't recommend this, if you're looking to actually make money to pay bills, or even eat!
So what is domain parking? Well, domain parking is pretty much the same idea as PPC except you receive a much larger percentage, and can actually make enough money to live on that money alone. Say you sign up with a domain site (I'll list a few in a second), you can then take your existing domain, and point it with DNS settings to the parking site.
Once you do this, you can start getting traffic to the domain name, and you can start making money every time someone either does a search, or clicks a keyword/result. The domain parking sites are pretty cool because they give you all sorts of options to work with such as categories for your domain, keywords, meta words, templates and more. This type of parking usually gets the feeds on the domains (the ads and such) from sites like google, ask, or yahoo!
So when you send people to your search engine and they do searches, sites like Yahoo will pay the parking program, and you will receive a percentage as well. These percentages can be very low from 5% on up top 90% depending on what site you decide to go with. So, why doesn't everyone just pick the sites with a higher percentage?
Because there's a little thing we like to call CTR click through rate and CPM cost per thousand. These two attributes are what really decide on how much you make. The website can offer a 99% share, but the CTR and CPM could be really low which means you would make less money than you would, at a domain parking site with a medium share of 50% but a high CTR and a high CPM. It's all a science and there's no real way to figure out what site is the best, and how much money you can make.
The best thing you can do, it trial and error. See what site fits with you, which sites make you money, etc. If you have 10 domains, don't park them all at the same site. Pick 10 or so sites and see which ones do better at site a site b site c, etc.
So how do you find these "domain parking" programs. Easy! Simply look for Domain Parking Programs or Domain Parking Sites, or you could try these sites out. It used to be there were thousands of these sites but now only a few that are legit remain. I make no guarantee that you will make money at these sites, I'm simply here to tell you what domain parking is, tell you some of the stuff I know, and show you a few sites you can check out.
Parked (the best site ever)
NameDrive (good for adult names)
Again, that's just a few sites you can check out. If you're looking for more, I suggest going to NamePros or DNForum and look through the different threads they have and see what different people say about different parking sites. Good luck in your search, I hope you find what you're looking for, and remember to always read and follow the TOS guidelines. They are there for a reason!