Add functions and events to SharePoint form fields

http://webborg.blogspot.com/2008/04/add-functions-and-events-to-sharepoint.html
http://sharepointspot.blogspot.com/2009/03/found-way-to-sharepoint-field-using.html
http://blogs.msdn.com/b/sharepointdesigner/archive/2007/06/13/using-javascript-to-manipulate-a-list-form-field.aspx?PageIndex=8#comments

For Loopup fields more than 20 items, MOSS will render differently, instead of select tag, it will render as input


http://www.sharepointboris.net/2009/10/sharepoint-lookup-field-how-does-it-work-and-how-to-add-javascript-event-handler-function-to-it/
http://www.agorainc.com/blogs/post/Binding-onchange-event-to-SharePoint-Lookup-column.aspx