http://www.ephpod.com/ - And it supports Windows 98 (SE)!

EphPod is a full-featured, easy-to-use Windows application that connects with Apple's iPod. With a FireWire card and EphPod on a PC, it takes under 30 minutes to transfer 1,000 songs to an iPod. In addition, EphPod supports standard WinAmp (.M3U) playlists, includes powerful playlist creation features, and will synchronize an entire music collection with one click. It imports Microsoft Outlook contacts, in addition to allowing users to create and edit their own contacts. EphPod can also download the latest news, weather, e-books, and movie listings to an iPod.


http://www.gtkpod.org/about.html - Linux program - gtkpod is a platform independent Graphical User Interface for Apple's iPod using GTK2. It supports the first to fifth Generation including the iPod mini, iPod Photo, iPod Shuffle, iPod nano, and iPod Video..

http://www.vonnieda.org/vPod/ - vPod is a program for transferring music to your iPod from Windows. It presents a unified view of all of your music and lets you see what is and what is not already on your iPod. I think that it's a much more intuitive interface for managing what is available on your iPod than the existing solutions.
vPod is free software. It is licensed under the Free BSD license so that as many people as possible can benefit from it.

Floola - http://www.floola.com/modules/wiwimod/ - Floola is a freeware application to efficiently manage your iPod or your Motorola mobile phone (any model supporting iTunes). It's a standalone application that can be run directly from your iPod and needs no installation under Linux, Mac OS X and Windows (Windows Vista is supported).

Floola supports all common used iPod features including artwork, podcasts and smart playlists! It's also able to convert audio or video incompatible with the iPod so that you can copy almost any file to it. It even allows adding youtube and myspace videos just entering the page url!

Media Monkey - http://www.mediamonkey.com/- Synchronize with iPods, MP3 phones and other Portable Audio Devices in seconds. Simply configure MediaMonkey once, and then click the Synchronize button to synchronize tracks and related properties including Album Art, ratings, play history, and playlists with a broad range of portable devices*. With Volume Leveling, the tracks will even play back on your device at consistent volumes!