iLife comes free with every Mac and is so good to use that no one thinks of these apps in the same way as the free programs the the PC manufacturers giveaway. iLife really is totally useful and enhances the user experience and value of having a Mac.
iMovie is totally reworked from iMovie 08 which was a backwards step in that edition from iMovie HD, though now in iMovie 09 it is looking good again. Seems that a time line is not totally necessary when you have the precision editor available.
Garageband just keeps getting better and better. Not many know that you can take something from iMovie and put in Garageband to add music track, voice overs and any other sounds you wish.
iPhoto With Face recognition and Places the geo-tagging, it is pretty amazing for organising your photos.
iDVD Is useful now but for how much longer? Soon we will not bother with DVD and everything will be an electronic file residing on a hard drive or memory stick. But with iDVD you can make DVD with chapter markers and if you give a DVD from this to your mom, she will totally love it. It is amazing how professional it looks.