Transcriptions, arrangements etc.
Gigue by Jean-Mari Leclair (clarinet and piano)
It was typeset from an old handwritten copy and I have no idea which opus it may be from since I couldn't find the original violin version on IMSLP or elsewhere, or even if it's really Leclair (though the stye is consistent with his other works). Regardless, it's a pretty, even if challenging piece.
A sonatina from Weber's Six Pieces collection, made into a solo piece.
Tico Tico no Fuba
The ever popular, archetypical samba by Zequinha de Abreu.
An oboe piece by Sergey Vasilenko, a soviet composer (the original russian title is “Песня на рассвете”)
Note that this piece is most likely not in the public domain since Sergey Vasilenko died in 1956. I have no idea who you should talk to if you want to license it. It's a nice piece though and I'll rather push the limits of fair use to spread it.