I'm working on a site at the moment that loads all of its browser popups by using page methods. This approach works but it's starting to get messy. I also view page methods as ways to perform small tasks, username availability comes to mind.
What other options are there besides page methods and the update panel?
PageMethods sounding fine to me (which are essentially Webservices).
You could pull more data per request and use cache more. You could build a better JavaScript wrapper which satisfies the need for more tidiness.
You could choose another library: http://stackoverflow.com/questions/861784/how-to-call-a-web-service-from-jquery
You should look at the JQuery ajax functionality. http://api.jquery.com/category/ajax/
You can point the url of the AJAX request to an aspx page or an html page or pretty much any web resource that you like, as long as the request is handled on the server by some kind of HttpHandler. And as long as your callback handler is able to handle and display the returned resource