So you have one drive already set up as a TimeMachine drive, but now want a extra backup of just your Photo's and Music on another drive like in case you need to switch to a Windows PC and need to access the data (TimeMachine basically "traps your data) or having a extra backup. Smart choice.
you should look at "Storage Drive" here
Also learn how to format the drive properly for various uses
Also you can drag and drop folders like Pictures and Music to a external drive to copy them.
With iPhoto, Apple likes to give the appearance the pictures are stuck in iPhoto, however you can right click on iPhoto Library and "show package contents" to find the folder called "Originals" which contain all your original pictures.