Until we get official MicroSIM's for our iPads I just thought I'd share that Deal Extreme have the adapters and templates in the following product:

http://www.dealextreme.com/details.dx/sku.16947

Ignore the actual 2in1 device and you'll see for your $2.90US you get two MicroSim adapters + two transparent sticker templates to help you cut your normal SIM accurately down to size.