The mini ajax site offers some great code samples and examples. There are some techniquest that can be integrated by anyone who has a little bit of code knowledge. So, if you have wanted to play around with Ajax, or Prototype or Script.aculo.us, take a look.
When integrating these ‘cool’ functions, ask yourself if they are really necessary, or if they make the user experience better. Consider whether you are doing it to just ‘do it’ or if they really serve a purpose for your site visitors. There are always trade offs. BTW: According to someone who Brett Tabke knows within a major ISP, this whole Web 2.0 thing is for the female demographic. I feel that is is more site specific than that, but if your site caters to the female demo, perhaps you should consider working with some of these scripts to see how your users react.
Good luck and have fun!