F-Secure has open-sourced its Sandboxed Execution Environment

Cuckoo is a full-feature behaviour analysis platform which supports extensions via plugins.

SEE is a modular and flexible framework for building sandboxed test automation against generic software.

Focus of SEE design is to speed up the development of behavioural analysis platforms. It allows to choose between several different sandboxing technologies and provides a plugin-based event-driven architecture in order to control them.

SEE is for developers and not for users. If you want an out-of-the-box solution for analysing malware you choose Cuckoo. If you want to develop your own analysis platform, you better try out SEE.