I thought I'd share a few of the awesome Vocaloid youtube video's I've found. Enjoy!

Kaito-Paprika Susumu Hirasawa song
this isn't a singing one but one with cute animation
Miku-Ave Maria
Miku-Tetris Theme
Cute animation to the PreCure theme
Miku-Country Road by John Denver
Miku-Fly Me to the Moon by Sinatra
Miki,Len,Rin-Pachelbel's Canon
Miku-Final Fantasy collage song
Vocalrozenmaiden is a fun animation video to watch
Miku,Len,Rin-Circus (Has some neat original animation

That's it for now, but believe me, I've got like 20 more or so that I'll be posting at some point.

Moetron Vocaloid info and weekly rankings
this is a neat site I like it alot. You can check out collections of the top ranking songs and they always have nifty pictures. Currently they have 45weeks logged among other news and such

Len,Rin-Gundam Seed song(don't know the name sorry)

Kaito and Rin Sing Paprika ending this one has some cute animation

Rin, Len, and Miku original song Kienai Hitori again, has some nice animation has some lulz at the end, you'll know it when you see it.

Not the vocaloids singing but it's so SOOOOO cute! Trust me! and it's a commercial parody of all things, imagine that.