iPhoto is a great app that allows you to manage, organize, edit and share your photos with ease. The tools that are built-in to iPhoto are pretty amazing for an app that comes bundled with every Mac (search for "iPhoto" in Tech Talk to learn more). There are some great ways to keep your photos organized, making it easier than ever to find the photo you're looking for quickly. Albums and Smart Albums are two tools that help with this.
As nice as it is to use Albums and Smart Albums to keep your photos organized, sometimes you just need a little more separation. For example: two people use the same computer under the same login, but want two different iPhoto libraries. Another example: you're a professional photographer, and would prefer to have separate iPhoto libraries for each client so that clients don't see other clients' images. Creating and using multiple iPhoto libraries is super easy... if you know what to look for.
When you open iPhoto by double-clicking the icon, it will open the default library found in your Pictures folder. To create a new library, Quit iPhoto, then while holding down the Option key, open iPhoto again. This time, you will be presented with the following screen:
At this point, you can either create a new library file, or open an existing library file. As you can see above, I only have the default library file to open. If I had crated other library files before now, they would be listed as well. When you choose to create a new library, it will ask you for the name of the new library file and the location (which is in your "Pictures" folder by default). Once you have created the new library file, you will see an empty iPhoto. It's time to start using it. Remember: because this is a new library file, you won't see any of your other photos here.
If you close and re-open iPhoto at this point, it will automatically open the new library (iPhoto defaults to opening the last-opened library file). To open another library file (for example, your original file), simply open iPhoto while holding down the Option key. I will now see both library files available, and I can pick and choose the one I want to open.