Boy, now thats a broad range of things, anything that would be social oriented and/or technology oriented seems to be the most popular things at the moment. Just take a look at all the kids addicted to myspace and ipods/telephones.
I own a domain named TEEN UNIVERSE .com but in spanish, UniversoTeen.com Well, the teen market its pretty big, it works stuff like: Celebrities News, MySpace stuff, Music, Movies, Girls Stuff, Boys Staff, Sexuality, Games, and so many other things. I can guide you on this if you need help. Just PM me
Music College Info Social Networking Sites All those sites that allow you to improve you profiles at Myspace and Facebook Sports Beauty Think of people that age that you know and see what they are interested in. I think this groups is easier to target with the internet. Being online is a part of their everyday life. ~H
Kids this age like to trick out there social networking pages (for dating and personal relationships), computers, cell phones, cars.............they like their music and movies............ they are thinking about college........... Check out what is already be advertised on site with similar demographics. Don't worry about competition - just be a better marketer. Server the target market exactly what they are looking for, when they are looking for it and when they are willing to pay for it. College Scholarship Webfetti, Zwinkys, etc Busted Tees College Humor Cell Phone and Ringtone Some may be interested in work opportunities
17-20 year olds often find themselves short on cash. 'Cool' games and things that are funny spread through social networking sites like wildfire, especially if it is something they can compete against their friends with.
As digitized already pointed out, offering free or cheap, quality products and content will go a long way in your chosen demographic.