Machine / Server Virtualization
Qemu* with Kqemu Accelerator by Fabrice Pascal
VirtualPC* by Microsoft
VMware Player/Workstation/Server by VMware
Desktop Virtualization / Thin Client
AnywhereTS requires 48MB (64MB) of RAM and 12MB (16MB) of HDD space.
VMware OpenView / Thinstation requires 80MB (96-128MB) of RAM and 30MB of boot CD space.