For iPhoto, this is of critical importance in that any image added to iPhoto is copied into the library (unlike iTunes, which simply stores a pointer to the original file). Considering what can be done with an image in the library, this makes a lot of sense -- it will make more sense once Apple supports multiple libraries in a more traditional multi-document application approach.
To change the default file store location, go to terminal and type:
defaults write com.apple.iPhoto RootDirectory /path/to/desired/locationTo remove the change default:
defaults remove com.apple.iPhoto RootDirectoryIf anyone wants to implement custom exporters and formatters, it isn't hard....
[Editor's note: Congrats to bbum for the first iPhoto tip, a mere 12 hours after its introductiion!]

