I have a small contribution to make:
http://www.mediafire.com/?ky2dyggq2gu
It's the song "Nyamo-chan no Uta ~Love and Peace~", Nana's character song from Love Hina. I dont know how rare it is, but I've been listening to this *years* before I even really heard about Nana, back when I was a big LH fan, so I found it pretty interesting, seeing as she's one of my favourite artists now XD