I'm using SharePoint 2007 and I'd like to configure a task list to send an alert to the assigned-to user(s) and assigned-by user when the due date for a task is approaching (for instance, when the due date is 3 days away). From what I can tell, this option is not possible on the Alert Me page of this task list, so if anybody knows another way of doing this then I'm all ears. Thanks in advance!
you can use nintex workflow which is suggested by most of the developers in sharepoint which is used to have business related process being automated.
In your case you can frame a alert with email on specific duration so that you can get all assigned people can get a mail regarding the task they are assigned to.