QEMU

QEMU is an open source emulator and virtualizer. It is an alternative to vmware or oracle's virtualbox although they are only hypervisors.
QEMU also supports android and can be used as android emulator for debugging and testing apps.
Some features listed on its website:

• Run operating systems for any machine, on any supported architecture
• Run programs for another Linux/BSD target, on any supported architecture
• Run KVM and Xen virtual machines with near native performance

QEMU is free and open source software. You can edit the software according to your needs with little bit of technical knowledge which makes it great of technical users and organizations.