Evan Mullins points out: "The world has been excited by html5/css3 recently and has been pushing limits and experimenting. It’s been exciting and funny at the same time – most of the things that are amazing people in html5 experiments have been done 5 years ago in flash."
And he has a series of very simple generative "art" apps coded in as few as 15 lines of Actionscript.
intro,
line-width, & color
Mike C. sent me the following link, full of cool new HTML5 / Canvas effects (all JavaScript, no Flash or other plugins)
http://www.nihilogic.dk/labs/pocket_full_of_canvas/
I tried implementing one of the examples but couldn't figure out how without rewriting a bunch of the code, so I modified something from this site to make the HTML5 banana above.

The Wikipedia entry for the Codex Seraphinianus states: "The Codex Seraphinianus is a book written and illustrated by the Italian artist, architect and industrial designer Luigi Serafini during thirty months, from 1976 to 1978.[1] The book is approximately 360 pages long (depending on edition), and appears to be a visual encyclopedia of an unknown world, written in one of its languages, a thus-far undeciphered alphabetic writing."

The book is truly fantastic, full of animals, inventions, customs, cities, and other aspects of a fantasy world. The idea of an encyclopedia of a wildly different fictional place created in a mad-up language reminds me of the Voynich Manuscript but while that seems to have been a hoax, the Codex Seraphinianus seems to be 'merely' an art piece.

The look is quite similar to the movie "Fantastic Planet" from 973.
sixfoottallrabbit made an implementation of Conway's Game of Life in HTML 5. (more)
Related is this First replicating creature spawned in life simulator
Sweet Child O' Mine (Swing Version) by plamere
swing by antireality
The Swinger is python code that time-stretches the first half of each beat and time-shrinks the second half, giving any song a "swing" rhythm.
http://musicmachinery.com/2010/05/21/the-swinger/
more:
http://soundcloud.com/plamere
http://gizmodo.com/5547876/a-python-code-that-makes-any-song-swing
I don't normally broadcast this kind of thing but it was one of those situations where I had been gesturing rudely at the computer screen for hours on end before finally having the revelation: when validating a web form with JavaScript, it will fail if you have hyphens in the form names.
I've been doing this kind of thing for over ten years and I don't recall this ever coming up before.
Normally, when you validate a form, if the code detects a problem (e.g. an empty field that is required, or an email address that's not a real address) it aborts the submission of the form, thus saving time both for the user and the server. But the form I was working with defied this basic rule - it always successfully detected the problem, but then went ahead and allowed the form to be submitted anyway. Removing hyphens from the field names resolved the issue.
Special characters are typically things such as apostrophes or dollar signs, characters that have meaning in cod as well as normal language. But I had thought hyphens were safe.
The surprise to me is that, while googling the keywords almost always provides the needed answer, this one came up with nothing. It felt like I was back in 1996 or something.
I hope future generations will benefit from my wasted time.
Roedy Green has a funny (and very long) guide called How To Write Unmaintainable Code [Ensure a job for life ;-)]
Misleading names
Make sure that every method does a little bit more (or less) than its name suggests. As a simple example, a method named isValid(x) should as a side effect convert x to binary and store the result in a database.