Proprietary HDLs

Agility
Provides software technologies for MATLAB to C and C to FPGA synthesis and a rich portfolio of synthesizable algorithmic functions and FPGA hardware platforms.
http://www.agilityds.com

Agility: DK Design Suite
Alogorithm to implementation using Handel-C to FPGA.
http://agilityds.com/products/c_based_products/dk_design_suite

AHDL
Altera's HDL.
http://www.altera.com/support/examples/ahdl/ahdl.html

bluespec
Bluespec adds extensions on to System Verilog to raise the abstraction level for complex control logic.
http://www.bluespec.com/