Qucs (also hosted on GitHub) is a “(Q)uite (u)niversal (c)ircuit (s)imulator” that lets you both layout schematics and simulate the represented circuit. Best of all, it’s completely free.

I’m not aware of any other tool that matches up with its capabilities. There are other tools, but they have downfalls as far as I am concerned. I only spent 5-10 minutes investigating each piece of software; at the end, I decided Qucs was the best fit for my habits. Your mileage may vary, so here’s a quick list of the other tools I looked at:

Neovim is a pretty cool successor to Vim, focusing on compatibility while adding asynchronous plugin functionality and trying to clean up the code base. Having been fed up at various times with both Sublime Text (2 and 3) and Atom, and after realizing how much development I do over SSH, it seemed reasonable to check out using vim (or nvim, in this case) as my IDE. The advantages essentially boil down to:

• Consistent IDE over SSH or locally,
• No need to ever use the mouse while coding (takes longer to learn, but is faster; this is aided by vim-easymotion and Ctrl-P),
• It’s been around forever, and frankly, probably always will be.

Some work really benefits from visual (mouse) input, but I have never found that to be the case while programming.