18012005 update: XmlHttpRequest seems to be a "better" way of doing things than remote scripting. http://jpspan.sourceforge.net/wiki/doku.php?id=javascript:xmlhttprequest and http://jpspan.sourceforge.net/wiki/doku.php?id=javascript:remotescripting enumerate the differences, as well as provide a comprehensive list of links.

http://www.peej.co.uk/articles/rest.html also advocates XmlHttpRequest over RPC-style calls. http://www.peej.co.uk/articles/rich-user-experience.html has more about this.

http://www.sitepoint.com/blog-post-view.php?id=171725 contains some insights on using XMLHttpRequest with Javascript closures.

Linklog of remote scripting resources:

Remote Scripting with Javascript, IFrames and PHP
http://www.phpbuilder.com/columns/vance20040507.php3

Remote scripting with javascript
http://www.dotvoid.com/view.php?id=13 and http://www.dotvoid.com/view.php?id=28

Cool LiveSearch feature
http://blog4.bitflux.ch/wiki/LiveSearch

Serverside autocompletion
http://www.sitepoint.com/blog-post-view.php?id=180147

Separating browser from resource
http://www.sitepoint.com/blog-post-view.php?id=176885

XMLHttpRequest
http://jibbering.com/2002/4/httprequest.html

Atom
http://www.atomenabled.org/

Javascript AtomAPI Client using XmlHttpRequest
http://www.isolani.co.uk/blog/atom/JavascriptAtomApiClientUsingXmlHttpRequest

jpspan, hooking up PHP and javascript
http://jpspan.sourceforge.net/wiki/doku.php

Qwad framework
http://www.qwad.com.au/code/doku.php?id=qwad_framework

JSRS
http://www.ashleyit.com/rs/main.htm

Somewhat dated article on DW about client-server javascript comms
http://www-106.ibm.com/developerworks/web/library/wa-exrel/?dwzone=web

JavaScript O Lait, providing javascript XML/RPC impl
http://jsolait.net/

Crouching javascript
http://www.sitepoint.com/blog-post-view.php?id=191776 and http://www.sitepoint.com/blog-post-view.php?id=192138

Apple Developer Connection about remote scripting
http://developer.apple.com/internet/webcontent/iframe.html

Pushlets
http://www.pushlets.com/

ECMAScript library acting as a cross-browser wrapper for native XML APIs
http://sarissa.sourceforge.net/doc/

Side-note: PHP developers are right out on the cutting edge of Javascript and DOM manipulation, getting standard browsers to do amazing stuff. Where are the Java folks?