Can I regain Garage Band (MAC) after deleting it?

I am trying to free some space on my start up disk. I want to delete programs I don’t currently use. However I would like to know if I decide later on that I’d like to use them again, is it possible? Some of the programs I want to delete incl:
– Garage Band
– iChat
– iMovie
– iWeb

Are they free downloads?
Do they come on the start up CD I received when I first bought my MAC?

Thanks! :)