What kind of sites do your run? There are a ton of ways to make a profit on individual sites, but its difficult to give you ideas becasue we dont know what kind of sites they are.
1.) Advertising. Already been mentioned, but you can do more than banner ads to sell advertising. A simple 'This page sponsored by Thissite.com' text link at the top of the page can get 30-40 bucks a month on a busy site.
2.) Merchandise. Create and promote merchandise for the site. If you have loyal fans, they may want to wear your gear. Cafepress is a good start, but expect to only make a dollar per sale. If you have some money to invest get some basics printed and sell those yourself. T's, hoodies, and hats usually. If you do sign up on cafepress you can enter my ID ' westcoast ' and I'll get a referral.
3.) Subscribers. I operate a message board with 8200 registered members and we offer various levels of subscriptions. We offer 4 packages, the cheapest runs 1.50/mo or 15 per year and you get rights to an avatar, signature pictures, and access to a special subscriber forum. Next one gets all the level 1 plus access to a photo gallery. Level 3 gets all of 2 plus an @s-series.org email address for $5/mo or $50/yr. The ratio from registered members vs subscribers is horrendously low, but we do make a couple hundred a year off of that option. Not a lot but it helps to defray some out of pocket costs.
4.) Donations. Im not one for begging so I don't make use of this option. I would rather offer someone something in exchange for thier money, but if your visitors are loyal they may donate to help keep the site running. I've seen one site say they needed help and some donations and they had over 20 guests donate over $50 in about 2 weeks. There were a ton of people who donated total, and all in all I think he raised $7K in less than a month.
5.) 50/50 Raffle. This only really works on a site with several thousand unique visitors a week. Set up a paypal account, tell people you have 100 tickets to sell at $5 a piece, winner gets 50% of the proceeds. Its good because unlike a giving away a prize you're not worried about recouping the money you spent. Also anyone would like to get cash as opposed to some lame prize. Be wary of local laws (gambling and whatnot)
With any of these ideas, people need to be cautious of legalities and taxes. Cafepress reports your earnings to the feds. Make sure if they report your earnings you report it also. If they find a discrepancy they will make your life a living hell, so i wouldnt even risk it unless it was 100% untraceable.
These are just some ideas. There are a ton of ways to make money, and the more creative ones are usually the most successful. People will be more willing to spend thier money on something rare or odd than they would on someone who just throws up a paypal 'Please donate to my site' link.
