Folder Lock is a security utility that password-protects just about anything on your Android device. It also includes a very basic browser which enables you to surf anonymously.
To protect files, login into Folder Lock and it will automatically detect photos, videos, notes etc on your device. You can then group items or photos into a folder you want to protect. Access to the files is then only possible with a password.
Annoyingly you can't protect SD card files though - only those on your phone.