I did domain parking at goDaddy for a while. Actually, it's called cash parking there. You pay a small fee to sign up and enter your domain names that you want to earn cash on. Domain names rich in keywords get the best results. goDaddy then changes the DNS servers to point to their cash parking servers. They display ads on your domain and you get a portion of the revenue generated from the ads. They have several membership levels. The more you pay, the bigger your cut of the ad revenue.

goDaddy has some nice templates to use so unsuspecting visitors think you're running a helpful links sites and not just some blatant ads.

It's not necessary at all to have web hosting. All you need is ownership of a domain name, but if you already have a site set up with a domain, it does not need to be hosted at goDaddy. All goDaddy does is redirect the DNS record to their cash parking sever and that displays the cash parking page. Your original site at your web host remains unchanged, although not viewable because your DNS records points to goDaddy. You can also remove the site from cash parking and change the DNS server back to your original web host any time you want.

It's a pretty cool way to earn money by actually doing nothing, but you'd have to have a lot of keyword rich domain names to make anything significant.