Have never heard the term 'sizzle' cards but like it!!
As a graphic designer, a lot of my day to day work is stationery and business cards. More and more clients are utilising their business cards in an advertising way, with things on the back like 'visit our website for current offers' etc
I have just been using the term 'mini cards' when discussing this with clients.
I did a set of mini cards for myself recently. They didn't have an offer but rather a stand out image and strap line. They have worked really really well for me and I've had a fair bit of business from them.
I have also followed up the mini cards with some direct marketing involving cards with jelly babies stapled to them (in small plastic bags). You'll probably understand why when you see my mini card below:
SIZZLE cards are a great idea and cheap to do, you can get 1000 cards printed for around