Streampad is a web music player. Its not just a music player that plays in your browser. Its a music player that plays the web.
Streampad can also be used to give you access to your own music collection when you are on the road. Streampad has a little server that runs on your computer that will serve up your music collection so whereever you are you can listen to your home music collection. For those of us that have terrabyte-sized music collections that don't fit on an iPod or a laptop.
Streampad is another example of the universal music player - it lets you play music from any source - helping you to play your music where ever you are (as long as you are connected to the web).
Streampad is currently a one man mission of Dan Kantor, formerly of del.icio.us.
By the by, Lamere's Duke Listen's! is a good read.