I have started with a new company and wanted to contact past clients and let them know where I am now, does anyone have a template or know where I can find a template that I can personalize?

Constant contact

I don't know what industry you are in but I would recommend one of two things. First, you could go and buy some cheap packs of thank you cards and thank them for their past business. Second, here is a template you could use if you just want to mail them letters click on this link to a template from microsoft.com