One of the interesting things about anime is that every series I've seen has it's own original sound track to it. Being a person with a very audio dependent lifestyle I have many of the soundtracks for several of the shows I've seen. Hack Sign, Love Hina, Cowboy BeBop, and Naruto are a few of my favourites. In my opinion a god anime must have a good sorting of music to help enhance the mood. dramatic parts are never as good without such music accompanying and the same is true for comical instances. However specifically in anime there is also (usually) the music specifically composed for the show with lyrics that reflect the story or a character. Some times the music is sang by an Idol some times its done by the very vocal cast. Regardless it's one of the features I love the most about how the Japanese tackle marketing for their productions.
The following is a song called "Kaze no Tadoritsuku Basho" from the show Kanon. It's not really promotional but it is a good song that was composed. It's stuff like this that I love so much about how they handle music for anime and the like.
Also on a side note the title "Kaze no Tadoritsuku Basho" is a bit difficult to translate. The best I can come up with is "Destination of the wind's struggle" since I really can't think of a way to say "tadoritsuku" 「辿り着く」 in english.
Please excuse the poor quality on this.