To learn more about jQuery, I recommend watching Stephen Walther's ASP.NET and jQuery PDC talk. Click here to download his code samples and powerpoint presentation.

Rick Strahl also has a really nice Introduction to jQuery article that talks about using jQuery with ASP.NET.  Karl Seguin has two nice jQuery primer posts here and here that provide shorter overviews of some of the basics of how to use jQuery. 

I also highly recommend the jQuery in Action book.

Hope this helps,

Scott