Don't get put off by its silly name, Mogopop is a fantastic new (and free) web-based service where members and visitors can create, publish and download multimedia content for their iPods. Content can include anything from audio, video, pictures, podcasts, to text. Imagine the geekiness that can ensue. It's almost scary.
Mogopop is great because you essentially create mini-websites for your iPod that you can share with all of your friends. Check it out at mogopop.com.