Hi Debra... welcome to the wild and wacky world of mystery shopping! :-D
Sounds like you are off to a good start. Tons of other companies out there, so be sure to set aside a bit of time each day to register for new ones so you can get more shops.
I think the amount of time required to register is the most daunting thing for people who are new, and one of the things that has kept my potential referrals from following through.
It would be really cool if all the companies in the MSPA could agree on a standard application form that potential shoppers could complete and submit everywhere.
Obviously some companies need to see writing examples and possibly other non-standard information, but that could be done with a follow-up.
It would make things SO much easier to get going, whether one is new or wants to sign up for a new company.
Have synthesizers, will travel...