Currently Being ModeratedFeb 4, 2013 1:49 PM (in response to Fenrisulven)
If you're using iPhoto, yes. Preview doesn't require that you create a library.
If you really want, you can control-click the iPhoto library and choose Show Package Contents, but shouldn't change anything inside.
Currently Being ModeratedFeb 4, 2013 1:55 PM (in response to Fenrisulven)
If you're using Picasa, why do you want to use iPhoto?
You can set iPhoto to reference the files outside the Library. For details on that check out this thread. Note the warnings.
For help accessing your photos in iPhoto see this user tip: