I've only ever recieve CD's from relatives and they tend to be by bands that I 'should' like such as Wolfmother, Jet, Coldplay, the Killers, etc.
If you are going to give CD's to people surreptitiously gage their reaction to bands/artisits that you play. In addition to this you should also brake into their place of dwelling and note what music they have, this includes CD players, hard drives and other portable music players. From this you can then gather a very good idea of what CD to buy for them. If it is a birthday check with fellow present givers (friends and family) to avoid doubling up. Feel free to gloat in present giving superiority.