No matter how many times I create web services, whether SOAP (ugh) or REST ... I never get over the amazement. They are SO COOL.
What I love is the hiding of complexity and technology. The consumer knows only a URI and gets back some JSON. No need to know whether the provider is Windows, Linux, OS/400 ... Commodore 64 ... whatever.
The consumer also doesn't know that your Windows server is picking up the request, querying a DB2 database on a mainframe in Toledo and a MySQL database running on a Linux box in Marlboro, then retrieving some NoSQL data from a CouchDB instance running in Paris.
So cool. I love that.
"Here's a URI. That's all you need."