The Sennheiser CX 300 is ideal for the iPod. Clean music playback plus a unique design. The price is 30 euros more than fair. Sure, an earphone can never "true" on a pair of headphones (eg HD 600) come close, but an MP3 player is not a hi-fi system. The three different sizes of ear adapters are very well made and also ensures that ambient sound is somewhat mitigated. While this never replaces a system like NoiseGuard but eg in train quite pleasant.
The CX300 is a well-to recommendatory in-ear earphone very beautiful the harmony in my opinion with the iPod.
(Only criticism: The packaging is really extremely difficult aufzubekommen Since Sennheiser has operated absolute over-engineering..)