Where to advertise photography workshops?

[johnembrace]

Hello,
I'm starting to orgainize nature digital photography workshops for the not for profit company i work for (Embrace Cooperation Ltd), to provide a new income for the charitable projects, we run. We have been running free nature photography workshops and they have had lots of interest and always over booked. But as we are now asking people to pay I was wondering if anyone has any advice as where we should advertise either online or via magazines to make your workshops successful. Any advice would be much be welcome.

Thank you John

Website we have set up to advertise workshops:
Photography Embrace Workshops