If you want to start on application on the Mac at a scheduled time, you can do this using iCal. Just create a new event in iCal and include an alarm for the event by changing the alarm type from None to Open File. When you make this change, an additional pull-down menu will be shown below this that allows you to select an application. The default that is shown is iCal. If you click on this you'll get an Other... option. Select this and you'll then be able to browse for any application you like.

You can use to this to open an application at any time in the future. You can even create a reoccurring event so that an application gets opened on a regular basis.