Applespider said:
You could move all your 'hidden' pictures to a different roll and then view by roll. That way if you keep the roll closed, people won't be able to see it.
Or use iPhoto Buddy and keep all your dodgy pictures in a different library.
You can also select different libraries on
starting up iPhoto with holding down the Command key (or is it Alternate?). This way, a Folder-opening dialog opens, and you can choose alternative libraries.
I think you should do the same
again when you are done with your pictures, as iPhoto will open with the last selected library.
(Btw, that's one way to bring back an already-existing library in iPhoto, or move it to another HD and still use it).
NB: the files will not be hidden on your HD though, anyone can trace them down easily and open them without iPhoto.
Other mentioned options are arguable, as you will always see all the pictures if you check the whole library, with or without rolls.
To efficiently hide photos, er... Compress them in an encrypted file ?
A!