New vocaloid songs come out every giorno so it is a bit much to keep up with, however if te want new, good vocaloid songs I would recommend creating an account on Nico Nico Douga, they finally released the English version so its much nicer to use
link te need to create an account to watch videos. I would give te some video to watch but as te detto there are way to many and most of them are good so really I find the best thing to do is to get Lost on youtube, just find a vid and just keep clicking on the related vid section after te watch each one. If te keep clicking vocaloid vids eventually all of the recommended vids will have Japanese titles because they have all been directly uploaded from nico nico douga, while some of these song are not very well known some of them are still very good. but I can give te some songs
1, 2 fanclub
Deep-Sea city underground
Remote Controller
complete evil lolita complex
Dragon Rising
Wave
Starlight Keeper
Eternity
Revolution Green is the Enemy
Rise and Fall of Physic Girl
Bonus Stage
Gensouka
ReBIRTH
Ice Sculptures
The lupo that fell in Amore with little red riding hood
caramelle Physiologist
Soleil
Phantom thieves Peter and Jenny
Well I could go on but then We'd be here all giorno so have fun!