gschem is a free schematics editor and is part of the gEDA project. I found gschem fairly intuitive and easy to use. The first thing I did was to create the custom symbols for my components and add them to the gchem config file. After the components were created and loaded, I simply added them to the project and connected the pins.

More information can be found on the gEDA wiki: http://wiki.geda-project.org/geda:gschem_symbol_creation