I've search them all up for a 1000 times. Now I'm going to write them down as reference. This post will grow in the next few months.

Remember do not forget to set the behaviorId of the control. 

References:

CollapsiblePanelExtender
Expand:

• $find('BehaviorId')._doOpen();

Collapse:

• $find('BehaviorId')._doClose();

• $find('BehaviorId').collapsePanel();

ModalPopupExtender
Show popup:

• $find('BehaviorId').show();

Hide popup:

• $find('BehaviorId').hide(); 
  

When surfing around I found this great range ASP.Net controls.  Obout.com offers a great variety of ASP and ASP .Net controls. The controls are Cross-Browser (including Safari  and Opera).You can download the obout Suite for .Net 2.0. The suite contains the following controls:

• TreeView  (recommended)
• Grid
• Editor
• Spell checker
• Calendar
• Easy menu
• Combobox
• Slide menu
• AJAXPage
• Two colors menu
• Splitter
• Super button
• Tree_DB
• Autosuggest
• Show
• Flyout Window
• FileUploadProgress
• Slide Panel (with Slide menu)
• TabStrip (with Easy Menu) 
• Context menu (with EasyMenu)
• Toolbar (with Supper button)
• State Selector (with Combobox)

There are loads of examples on their website. So go check it out!