Altera Corporation

Free
Builder DSP allows you to go from system definition/models
Free
Quartus® II software is number one in performance and productivity
Free
Simulates field-programmable gate arrays with better & faster simulation tools
Free
The solution that enables the designers to target low-to-mid density FPGAs and CPLDs
Free
Nios II is a set of powerful commands to manage build options for applications
Free
Handles and incorporate programming data
Free
Creates, updates and manages hardware designs