Has anyone created some type of contest for their customers?
Something like:
Each time you place an order, your email goes into a drawing for a $100 Gift Certificate.
I would like some feedback, or ideas on how to impliment.

Check the legalities in the state where you are incorporated. I would also do a search for the legalities as it relates to ecommerce - better safe than sorry. You might just have to post some legal boilerplate text as a disclaimer.

As far as implimentation - I would post it on your blog (if you blog)...put some text on your home page...post it on some chat sites relative to your site...