Everyone knows that iPods play music and videos, and if you enable disk use (in the Options pane of the iPod Summary window in iTunes), your iPod can store all kinds of files. But with the help of additional freeware and shareware apps, it's easy to extend your 'Pod's abilities in some pretty unique ways.
Sync Like a Pro
Soup up iTunes’ sync features with iPDA ($19.95), which transfers data from Entourage, iCal, Web-based calendars, Address Book, Stickies, and Mail; displays text files in half a dozen formats; and downloads RSS feeds, weather, and news. Especially valuable for Entourage users, it’s like having an assistant who also happens to rock.

iPDA's icon-based interface makes it easy to find exactly what you want.
Say It Instead
Also from ZappTek, iSpeak ($19.95) It uses your Mac’s text-to-speech capabilities to create audio files of your documents, Web pages, and RSS feeds, and then adds them to iTunes, ready for your iPod. Heading out? Tell iSpeak It your starting and ending points, and the app downloads driving directions from Google Maps.
Make a List, Check It Often
You spent days tweaking your latest playlist to sonic perfection. Wouldn’t it be great if you could back up a copy, in case some of the songs get removed from your music library later? ListSaver ($6) lets you back up playlists - or even your entire library - from either iTunes or your iPod, and then restore them later.
Back Up for Free
If all you want is to back up data from your Mac, look no further than iPodBackup (free). This app backs up your Home folder (excluding the Music folder - much of which is likely on your iPod already) on your iPod as a regular folder, regular disk image, or encrypted disk image. You can exclude specific items, and on your second and later backups, it only updates files that have changed. Use iPodBackup in concert with Do Something When (free) to run backups automatically whenever your iPod is mounted.
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If your favorite album is the Beatles' Let It Be...Naked, this DIY kit is for you.

Unleash your inner 6-year-old girl by playing dress-up with your iPod! These costumes are mostly handmade, include adorable props, and are available for every iPod model, including the mini and the shuffle.
Links:
[1] http://www.zapptek.com
[2] http://www.deadendsw.com
[3] http://www.amake.us/software
[4] http://www.versiontracker.com/dyn/moreinfo/macosx/23675
[5] http://www.iPodMods.com
[6] http://www.h2oaudio.com
[7] http://www.iattire.net
[8] http://www.zapptek.com/
[9] http://www.deadendsw.com/
[10] http://www.amake.us/software/