This has helped me alot so thought I'd pass it along.
(sorry if this sounds a bit long winded)
I use external drives and DVD copies to backup my photo files and I've been trying to figure an easy way to keep track of which photo is on what DVD, and to help me know which images need to be burned.Basically my work flow is to import to my main Lightroom catalog and backup to an external drive. After the import is finished I use Bridge to backup the newly imported photos to a second external drive.Next I'll select a group of files,send them to a publish collection to export to a hard drive as DNGs with imbeded raw files and burn these files onto DVDs as additional backups.
After I burn the photos to a DVD I'll select all of the photos I burned enter the DVD title in the Sublocation box of the Metadata Panel then save the metadata for the group. this let me keep a record of which DVD the photos are on by storing the DVD title in the files metadata.
What I came across is I can set the Sublocation as part of the Header information that is displayed when you use Expanded Cells and have " show header with labels" checked. I selected Sublocation, now when I'm in the Library module, if a photo has a DVD title stored in the Sublocation metadata, the DVD title shows up as part of the preview. Now all I have to do is look at the preview to know which DVD has the image I might need.To go along with this I set up a Smart collection to help track images that need to be put on DVDs by having it sort by file type and no DVD title. So far it seems to be working well and it is really nice just to look at any preview and know where I put the backup files and which files haven't been put on disks yet.
Hope this is helpful