VBox has...*looks in list*...nothing ATM. VBox can't directly use Windows guests from VMware due to the fact that VMware emulates an AGP vid card and VBox emulates PCI. A few Linux distros have that problem too.
VMware: Zenwalk 5.2, Mandriva One '09, Ubuntu and Kubuntu 8.04 (both for demonstration purposes), gOS, PCLinux '09 beta, Debian 4.0, Fedora 10, 64-bit Vista, a stalled LFS build, and a team comprised of Windows Server 2003 & a pair of XP installs as a network sandbox. In addition, I have a copy of ESX Server which was an attempt to host VMware machines without having to use VMware Server (as you can't have both Server and Workstation installed on the same machine). Haven't had time to pursue that further but I was amused to find that it's just a stripped-down Red Hat. I previously had PC-BSD and Solaris 10 installed but didn't really get much mileage out of them.
Oh, and I have a certain other OS that isn't Windows or Linux which shall remain nameless...