Depends on what exactly you want to move.
1. File -> Export to folders in the Finder, then copy the folders to the other machine and import them. Depending on your choices in the Export dialogue this will get you the photos, but no versions or edit history and miss Faces at least.
2. Link the two machines together and use iPhoto Library Manager to move the images, plus all metadata, versions and metadata between the Libraries.
3. If you have the latest versions Apple's Aperture and iPhoto then you can open the Library with Aperture, export the Events as a Library and then copy them to the other machine and import that with Aperture there.