Others have talked about these things before, so this really isn't anything
new.

Recently, I found a Youtube Video, from HumanHardDrive, that talked about
a Specific Circuit Simulator.

I say it that way because it's not "real clear" that the name is? (you
will see in the next few sentences.)

It is Java Based, and the source is available as well.
There are certain aspects of the User Interface that I don't think are that
great.

Overall though I think it is actually pretty cool!

The Jar File is "Circuit.jar".
The Window Title, when it opens is "Circuit Simulator v1.6a".
The link on the Website to the supporting page is called "Analog Circuit
Simulator Applet".

and

The Name for that supporting page is called "rtds: Real Time Simulator".

The Youtube guy just calls it "falstad". (I think?)
Paul Falstad is apparently the main person behind it.

So here's the link if anyone is interested:
Falstad's Circuit Simulator

Normally what use are a Spreadsheet and Python Script to work
through electronic formula's for me. (Likely I will still keep those
around.)

This though is pretty interesting, and I am finding it useful.

I don't think this wiill work to simulate and entire complex circuit, but
it works really well for simulating various aspects of circuits and less
complex circuits.

There really isn't anything that is really MCU Specific. (There are TTL
Logic Levels though.)

It is also interesing that there are several, well dozens, of pre-built
circuits to browse through.

I am not, necessarily, convinced how accurate this is, but my knowledge on
that end is not complete enough for a valid assessment.

I just thought I would mention it in case anyone else is looking for
something to simulate analog circuits that you can play around with before
building them.

Has anyone used this one before?
Are there other Circuit Simulators that people here use?

I've used this simulator for quite a while. Downloaded it local to my PC and have it there at the ready whenever I need it. I haven't really used it for anything beyond simple current paths and quick resistor calculations but it comes in very handy for that. It is interesting to see visually how current flows through a circuit.