How can I copy a playlist from my iPod to iTunes?
There are several applications for doing this:
Yamipod
Yamipod is a freeware application that works on Windows, OS X, and Linux. It has a simple interface and looks very easy to use. There is a document on how to transfer songs from your iPod to your computer here. It is also an iPod manager and an alternative to using iTunes.

Transferpod

Transferpod is avaiable for both Windows and OS X. However, it is not free. It supports the iPod shuffle, the iPod mini, the iPod nano, the iPod classic, the iPod with video, the iPod touch, and the iPhone.
Key features:


iPod to computer transfer
Manage iPod playlists in an easy way
Organize entire iPod music/video for your convenience
Browse iPod file information in detail
Quick search your music and video file on iPod


iPod2iTunes
iPod2iTunes is for Windows. It also is not free.

Features include:


Connect multiple iPods.
Drag and Drop Songs, Playlists or Video   back to iTunes.
Move entire genres, albums and artists.
Keeps your playlists intact.
Enhanced searching and grouping of songs.
Find duplicate songs within iTunes and remove them quickly.
Optimizes iPod storage space.
Supports Virtual iPods.
Support for the latest 6th generation iPods.   (excluding iPod
Touch/iPhone)