Monodraw is written in Obj-C against the AppKit framework and we always strive to create the best native experience.

This means the app is not portable as it is right now. But with the recent announcement from Microsoft about their support for Obj-C, this might be something that could happen in the future (MS does not yet support AppKit).

(Monodraw developer)

http://emacswiki.org/emacs/ArtistMode is clearly less featureful, but might work for less advanced use cases.

Less feature rich, but handy, is a program called aacircuits, for drawing ASCII-art circuit diagrams. It dates way back to the days of Usenet. I still use it to include small schematics in microcontroller source code. For instance if I figure out how to program a particular chip, I include a schematic of a circuit to "demo" the code.

I'd be shocked if aacircuits doesn't run under Wine on a Linux machine.

If you do perl stuff there is Asciio

http://search.cpan.org/dist/App-Asciio/lib/App/Asciio.pm

may help on Linux. But Monodraw looks nicer and more featureful and easier to install on Mac.

There's also http://rexpaint.blogspot.com ...I might eat my words on this, but I think it's by the creator of cogmind a rougelike in development.

JavE [http://www.jave.de/] is a java application with similar features.

+1/Like/Up-vote for that.