gnetman is a program which currently supports advanced SPICE netlisting from gschem (part of the gEDA tool suite). The primary use so far has been for complex IC design. Supported features include multi-level hierarchy, instance arrays, and buses. If you're just doing flat designs for PC boards or smaller SPICE simulations, the usual path is to use the spice-sdb netlister for gnetlist instead. The long term goal of gnetman is far greater. Two projects under consideration include a schematic generator, and a technology mapping back-end for Icarus Verilog. Basically, gnetman is a netlist manipulation database well suited for low-level manipulation of netlists.