SharePoint and Javascript

Using JavaScript to manipulate a list form field.

http://blogs.msdn.com/sharepointdesigner/archive/2007/06/13/using-javascript-to-manipulate-a-list-form-field.aspx

Hide a field from NewForm.aspx

http://edinkapic.blogspot.com/2007/08/hide-field-from-newformaspx.html

Using Simple JavaScript in SharePoint

http://www.sharepointkings.com/2008/06/using-simple-javascript-in-sharepoint.html

and few other links

http://sharepointsolutions.blogspot.com/2007/09/make-selected-links-in-links-list-open.html

http://social.msdn.microsoft.com/Forums/en-US/sharepointdevelopment/thread/941940cb-acef-434f-830f-233713773b99/

http://www.codeproject.com/KB/sharepoint/Control_validation.aspx