Autopsy

Digital storage devices are used for a myriad of purposes, from running programs to store files and photos to hide sensible materials.
Autopsy is a program that lets you explore storage devices and see what they were used for.

It has a nice graphic interface that makes it very intuitive. At start, it asks you if you want to create a new case, or open an existing one. In the first case, you will need to give it a name, assign a device to explore, and set other parameters. Then, the program will create a database and start exploring the device. When it's finished, it will show a list of found files in a single tree. This will allow you to get a snapshot of the device's activity at a glance.

This will allow you to detect if the device was used in illegal activities or if it contains improper material. Thus, if you are a law enforcement official, you can present the results as evidence. If you are a common citizen, you can still use the results to present a criminal case. A more mundane purpose of the program is that it can help you recover lost photos from your camera's storage device.

The program is free to download and use. A slight disadvantage I found is that the installation file is huge, so the download time can be long depending on your connection speed. Also, it can take a while to start since it needs to load several different files. Lastly, although it is very intuitive, you may need to devote a certain amount of time to learn all its functionalities.