I first encountered LSystems during university; this was in the mid-90s when fractals were becoming mainstream. However, it was only in 2009/2010, when I needed a toy problem to learn Scala and JAX-RS with, that I started writing renderers.
The current version lives at lsystems.houseofmoran.com and I encourage you to play with it! The URLs are designed to be easy to hack. For example, the path /F:F-%3EFF+(+F-F-F)-(-F+F+F):F/1.0-25.0-3.200x200.png breaks down into
Alternatively, just slap "/edit" on the end, to get an editable form. Here a few examples of what you can get:
See the following for a history its development: 2009-06-27, 2010-02-28, 2010-03-08, LSystem Explorations on Flickr and a sort-of screencast of a previous version, using Java2D, on YouTube.