Teens 4 hire
A searchable site that lists job openings for teenagers. It's free for teens (or parents) to create an account and search, however there are fees for companies to post job openings. This site caters to 14-21 year olds actively looking for a job. It separates the job listings by category and by seasonality (if the job is part-time, full-time or seasonal). A great site for teens who know what kind of job they want and are ready to start now.
Snag a job
This site allows teens to create a profile and search for jobs by category, zip code, or business name. They claim to be the #1 source for hourly jobs, and most of their listings are for openings in restaurants and retail stores.
Fun Advice
Searching for “teen jobs” on FunAdvice gives hundreds of results, mostly member suggestions on places that are known to hire teens. If you need to do some background research on job permits, legal ages to work by state, or other preliminary questions, use the site search to find fast answers.
The Riley Guide
This site is basically an All-in-One guide for the teen who's starting to look for a job. It has an already-compiled list of sites that post job listings for teens, plus loads of resources for teens who are just starting their first job hunt. Everything from salary guides to interview tips are in this guide.
My summers
A searchable site much like the others mentioned, but focused primarily on summer jobs for teens. The listings are mostly for openings at summer camps, for everything from camp counselors to activity directors. If you are a teen who loved going to camp as a kid, or are too busy doing the school year to hold down a job, this is the place to find that quick summer job.