ScottAndrew.com site has lots for new browsers
CSS Pointers Group dhtml resources  lots of things here
Bratta.com  scripts, demos, and tutorials + new bratta site DhtmlCentral.com
InsideDhtml.com
Dan Steinman's x/browser dhtml * getting a bit old now
— include external files  <layer><iframe> combo
Webreference.com - Dhtml diner code snippets site
— background resizer
— layer animation  N6 
— text fader code generator
— friendly page redirects
— low bandwidth rollovers css, dhtml, client side imagemaps
— positioned elements & os controls, applets & plug-ins
— dhtml dynomat generators for headline fader, menus, alert boxes
— scripting for 5th generation browsers & beyond
— scripting for 5th generation - part II
Builder.com @cnet
DynamicDrive.com  free code and discussion
Webcoder.com
Devhead -- dhtml  from zdnet.com
Web Monkey  dhtml resources

Hotwired.WebMonkey.com - Dhtml
— taylors dhtml tutorial
— taylor's five day dhtml tutorial
DevX - Project Cool
HtmlGuru.com
DhtmlZone.com
WebCoder.com
Beginners guide to dhtml

InsideDhtml.com - Cool Rule Tool gradient rule generator
How to Retrive Computed Css Values  with javascript in ie4+, n4, n6
SmokingGun.com  resize events, swapping, bookmarklets +

 Using <DIV> Layers 
OreillyNet.com - X Browser Using Layers Part I
— using layers part ii  moving on to show/hide etc

 Show - Hide of Div's  most of the hieretical menus and tooltips employ this
theFixor's WWW finds & Experiments
Basic positoned div demo
ParksComputing.com - Show/Hide

 Scrollers 
Assembler.org - Scrolling Div more there also - worth a look
DynamicDrive.com - Scrollers
— cross browser scrolling images  nice script with pause and link features
— horizontal & vertical  scrollers from dynamicdrive.com
— vertical with pause
DhtmlShock.com - Auto Looping  variation of David Miles
— horizontal scroller  variation of David Miles
gHtml.com  nice - but NO documentation = not for beginners DevEdge - Marquee Scroller   ie5+/n6/moz/opera   n4 
EarthWeb.com - News Scroller right to left

 Change Styles on the Fly  using scripts
Using Alternate Style Sheets
Developer.Apple.com - Modify Styles on the Fly
Modify Styles Without Using Links a project vii script  IE5+ N6   N4 Opera 
OreilyNet.com - Modify Styles Article
Mozilla Tech Note dynamically change CSS properties using x browser JavaScript
theFixor's WWW Finds using innerHtml

 W3C DOM Sources  
Standards Support in IE and Gecko Engines has charts on support
David Baron's DOM Test Results a work in progress
Dmoz.org W3C Dom Links
PbWizard.com lots of info + client side table sorting

 DHTML Libraries  multiple functions pre-built for you
DynAPI  continuation of Dan Steinman's project
DrClue.net DHTML Library some nice - but poorly documented actions
Polymath's DHTML Library 43 functions & containers in one file
Cross-Browser.com - DHTML API for IE 4+, NN 4+, Gecko, Opera 4+
SourceForge.net - relative layers library for creating dynamic designs that adapt themselves to the user's browser dimension ALL
DomApi.com  library & tutorials