I just installed arch on virtualbox to test it out but for some reason it's not displaying correctly ( here's how it looks: http://imgur.com/avbpxHE ) I'm using virtualbox version 4.2.16
Basically I just followed the beginner's guide and installed cinnamon after it was completed.
I also enabled 3d support, assigned 128mb to video memory and followed the steps here https://wiki.archlinux.org/index.php/Virtualbox#Arch_Linux_guests to install the guest additions. I think the problem is that the guest additions aren't working correctly since I tried to use the shared clipboard functionality and it didn't work either.