Good free or open source software for electronic schematic simulation and PCB design

Mmmm... LTSpice and gEDA, perhaps?

Google "free eda tools" or something; you'll get plenty of hits.

All of these are demos and have some limitations but they are free:

all in one:

schematic and sim

schematic and PWB layout

Good luck, Ed V.

Thank you very much for all pointers :) And I'll look at them later. Have been playing with Verilog lately which triggers the interest back to some good-old electronic theories. Wouldn't it be nice to write code in Verilog then _convert_ to an electronic schematic diagram for analysis, or even _produce_ a PCB from it and have a working circuit ... by using the same software tool! Guess there's no one tool does it all, right? If there's, it won't be cheap ... well, not affordable as a hobby ... for now.

Not really. Unless you're doing a really large Verilog design, it'll most likely fit into a single part (e.g., FPGA or CPLD), so there's little point in the guys who write Verilog synthesis & place/route tools to try to do PCB design as well.

The big-guns of HDL simulation -- ModelTech and Aldec -- do have integrated design entry & simulation, and you can probe around during a simulation on a "schematic" that contains, e.g., block diagrams of your Verilog modules. Although they're calling external programs to do it, they also provide seamless synthesis & place/route from within their IDEs. In general the best EDA solutions end up using different vendors tools for solving different problems, but try to tie them all together in a nice "flow."