How to load different parts of the page asynchronously instead of waiting for the whole page? - iGoogle style

I'm working on an ASP.net application in which 开发者_高级运维I've multiple web parts in a page. Each web part has its own data source pulling data from them and showing it. When a user tries to load the page I want to load the page instantly and asynchronously render all the web parts with the data.

But I see using Ajax I cannot initiate multiple requests simultaneously. But I can queue the requests and process them which is not going to help in any way since if any of the request is going to take long time all the subsequent requests need to wait.

Any ideas on how to achieve this behavior?