I've looked at a tool called FS_scan (http://clusterbuffer.wetpaint.com/page/File+System+Scan) that gives lots of data about files in a CSV format. That's only part of the puzzle of course.
I've worked at places that move files older then a year to tape. So the users run scripts to change the timestamp and they never get archived. Usually IT doesn't know what data is needed/not needed and can't arbitrarily set an expire date. I've seen places that use a disk hogs email. Without management support, users can ignore them.
Users see 1 TB drives for $100 and say disk is cheap, but someone has to buy them. Then they need a computer to plug them into. USB drives are slow, not designed for multiuser access and they're fragile.
I'd like to find a tool that finds "old" files and encourages the user to do something with it. I've thought about moving directory structures into a tier of folders and out of the main folders. Or emailing whoever owns a chunk of files periodically. Ideally I want something that gets users to deal with useless data without involving IT, new purchases or management dictum. I can dream
What do other IT shops do?"