One of the advantages of using iPhoto or Aperture is all the images are available in the media browser that is built into many OS X applications - all Apples iWork Applications support it, as well as Microsoft Office. Within the Application you can browse your library in the Application and even filter via a simple search field. Then just drag and drop to insert the image.
In the interest of "full disclosure" it should be pointed out that there is a difference between exported images from Aperture and using the media browser. Aperture maintains a preview image of each image version that is used within the application to display images quickly (without having to reprocess). When you select an image from the media browser that is what you get. When you export a version, it is processed from the original and you can generally get greater resolution. The resolution of the previews is settable in Aperture's preferences and should be large if one makes use of the media browser. Of course you then lose the feature of Aperture that its libraries are more compact than iPhoto's.