The fact that so many phones now include a camera is one reason that digital photography has become so popular. The iPhone with its built in storage is a perfect combination of mobile phone and camera, and it is very easy to build up a huge collection of photos as your travel around - but it is also very easy to lose track of what you have photographed and where.
Labelbox is a free app that may be able to help you out, making it possible to quickly and easy add labels to photos. Labels can be added to existing photos, or you can use the app to take new snaps and add labels as you go.
Labels can be swiped into place and can be positioned anywhere you like - add your text at crazy angles if you like. If you change your mind about positioning, a quick shake of your iPhone enables you to start again. As you would expect from any image editing app for iOS, Labelbox enables you to upload images to an online community.
There are nine different styles of label to choose from as standard, but more are available as in-app purchases. While these are cheap enough, if you plan to use the app purely for labelling purposes rather than creative venture, the free bundled options should suffice.