Fotos is a free iPhone app that catalogs your camera roll and albums and lets you add names to your images, making them easily searchable. It seems pretty basic, but Apple really doesn't allow you to name or rename images in the iOS version of iPhoto, which is a shame. "IMG_3561" just isn't that helpful. You can add some tags, but actually naming a photo appropriately is a really nice way to go.
Launch the app and browse photos and albums. You can select them all at once or pick-and-choose. From there you can rename an image and browse its metadata, including where it was shot. Any changes you make in Fotos do not affect the originals. You can create new albums or collections within the app.
To find a photo, just start typing its name and matches instantly appear.
In addition, the app lets you share photos through the social sharing services or email. AirDrop is also supported. If you mail a photo from with the app the name you've assigned goes with it, rather than the arcane Apple name.