Yes, it's true, Gmail can now play mp3s (http://www.shivaranjan.com/2006/08/23/gmail-now-plays-your-mp3-files/)! So if you wanna listen to music at work but aren't allowed to bring your MP3 collection in, just email 'em to yourself on a new Gmail account that you create just for this purpose.
Yes I did know. ;) I believe there is a grease monkey script that lest you embe it in other sites as well.
An age of miracles!