I have been looking at machinima music clips for some time and always love to see the creativity many people bring to what is just a hobby.
Again and Again
This music clip isnt strictly machinima in the traditional sense - it is using the tools in the Apple OS to build a video instead. That said, the clip builds to a rather mesmerising and artistic flurry of applications - very clever indeed. Bird & the Bee are a band from California, not sure though who made the clever clip which must have been far more work than it looks.
I came across the clip first on Gizmodo, but here is the youtube version:
WoW Video Comp
The Blizzard folk have just had a comp going for creating a music video for "Rogues Do It From Behind" using the World of Warcraft Engine. I hope such a competition will bring out some of the talent that has done these videos before and a whole lot more besides. Cant wait to see them.
Second Life Vids
The Second Life site has a Photos & Machinima section in its Showcase area, plus a spot particularly for music. There are plenty more on youtube etc for everyone to explore, but here is one in the set which shows off the Bartlett House (perhaps not a music vid - but rather cool for SL):