Solandra is my open source framework for creating algorithmic art (it would also work well for data visualisation) and I've updated the 'art' section of this website with a lot more Solandra content.
There are now several full tutorials, links to the main Solandra site and some information on how to get started.
I've also begun a Daily Sketches site. An open source version of this is ready to adapt as a template project on GitHub, if you want to set yourself the goal of creating one algorithmic sketch per day. This was inspired by Saskia Freeke's ongoing project.