VMware Workstation 7, now available, adds Windows 7 support and several new debugging features. It didn't officially support them, but Workstation 6.5 could already run Windows 7 virtual machines (VMs) quite well. In addition to official support for the new OS, Workstation 7 lets you run Windows 7's Aero graphics and other DirectX 3D features.
Workstation 7 also adds other features for those who use it for testing. It now supports assigning up to four CPU cores and 32GB of RAM to a VM and allows you to run vSphere and ESXi in VMs. It expands Workstation's Linux support.
VMware Player is a free alternative to Workstation that uses similar technology, but without Workstation's debugging features. Contrary to the name, you can use Player to create VMs, and like Workstation, Player has full Windows 7 support.