KSS International www.kernscheduling.com
They schedule for over 70 different mystery shopping companies. Be sure to register here and you will start to get emails of shops in your area.
Jobslinger www.jobslinger.com This is a great job board where schedulers from lots of different mystery shopping companies post their jobs.
MSPA The Mystery Shoppers Providers Association had a job board available. Schedulers post jobs here often. You can also search the companies list to make sure you register with more companies. www.mysteryshop.org
You may want to get your silver or gold mystery shopper certification while you are here.
Volition This is a must for shoppers. You can check the forums here too. This is a great spot for shoppers to join together to find out more about shopping. http://jobs.volition.com/exec/sfs/jobboard
I will continue to post information to get you shopping now, more often, and making more money!