Once I talked about 初音ミク before, and now we've got a great compilation album for this "artist": livetune's Re:package. Their sound is electronic and they use vocorder (autotune) to give more techno flavor to this vocaloid's voice. Melodies are so catchie and pop.
The result sound is somewhat close to what Yasutaka Nakata usually produces, so if you like Perfume, capsule or MEG I'd highly recommend this album for you. I'm listening to their complication all day long and it's yet never tiring me. You can find more videos by searching for livetune on YouTube.
Unfortunately their album was sold only at the Japanese biggest Otaku market Comiket and now at the Japanese small online store, but if you don't mind pirating there is a couple of ways to get them. Wish they release the album on iTunes store!