While travelling I nearly always was whistling some songs, that came to my mind. Sometimes because of what happend, sometimes because of what I was thinking, sometimes from another one, sometimes just for no reason...

The song, that accompanied me most of the time was
Wise Guys - Jetzt ist Sommer (Summer is now)

for all those who don't know this song: The refrain says:

Jetzt ist Sommer, egal ob du schwitzt oder frierst,
Sommer ist, was in deinem Kopf passiert [...],
Sommer ist, wenn man trotzdem lacht.
[...]
Ich drücke auf den kleinen grünen Knopf und die Sonne geht an in meinem Kopf

Summer is now, no matter if you are freezing or sweating,
summer is, what happens in your mind[...],
summer is, when you laugh even though
[...]
I just press the small green button and sun is shining in my head

Other songs:
Jovanotti: Io so, che non sono solo anche quando sono solo - e rido, e piango.
Red hot chili peppers: Perfect weather (while raining...)
Thanks one more to Winnie for the "wet sunshine"
??? - It's just per-er-er-er-er-erfect
Hooters - I'm alive!!!
Voices unlimited - Homeless
??? - Don't worry, be happy
??? - You can get it if you really want
??? - Raindrops keep falling on my head (also while raining ;o)
Avril Lavigne - Everything changes (when you turn around)
Noir Désir - Le vent nous portera

And some more I didn't write in my notepad

The most of them really tell something about the trip, don't you think as well?