Web services are hot and here is a fun way to learn about them ...

salcentral Web Services Brokerage has lots of web services you can play with, examine XML schemas, understand SOAP syntax. You can create web services of your own and even offer them for sale.

I remember years ago when the Web first appeared and I learned you could build web pages without any content of your own by hyperlinking to other sites. If was fun, exciting, and the Web was clearly going to make a big splash. This was before most people even knew what the Web was. I got the same feeling playing with web services on salcentral. Recommended.