Dave Ward has published a very good article about jQuery for ASP.Net developers on the MIX site. I found the part about unobtrusive JavaScript particularly useful.

With the recent improvements in ASP.Net for JSON and the ease of jQuery, all ASP.Net developers should embrace JavaScript for creating better user interfaces.

You can find the article here: http://visitmix.com/Opinions/What-ASPNET-Developers-Should-Know-About-jQuery