[apsurd]

REST and JSON hands down. So easy even I can do it. =) XML has been around but JSON is so much easier and more efficient that I tend to raise an eyebrow at services insisting I use XML =/

Start with basic GET services. Have users do admin stuff on your website. Then create embeddable widgets that present how to use your API to GET and display data from your service. Use javascript to fetch the JSON, and add it nicely to the DOM.

It's pretty fun actually.

[AmberShah]

I like most of this except the not supporting XML thing. Support both or just XML. There's just too much stuff out there already using XML that any big project already has the libraries, whereas JSON maybe not. So it's just more convenient to most people.