I was kicking myself last week because I lost one of the foams on my earbuds. So one ear was comfortable and one was uncomfortable while I listened to music. After a little digging, I found some forum posts in an iPod forum listing several places to get replacements. This afternoon I ran out to RadioShack and checked out their selection. For $2.99, you can get a package of four replacement foams that work just as well as the original ones. So if you lose the original spongy things from your earbuds, the RadioShack replacements will definitely do the job.