A handful of interesting projects, lesson plans, and tools for digital humanities information visualization (aka infoviz, sometimes aka data visualization).

Tutorials for making introductory information visualizations with the Processing language ("a language for learning how to code within the context of the visual arts")
We Feel Fine by Jonathan Harris and Sep Kamvar is a visualization project that scrapes current social media posts to explore human emotion in visually beautiful ways, and it's always been a hit with my students (the hard part is when they want to build something like it!). I couldn't get it to load in my browser this week, so it may no longer work.
- "The web's secret stories" TED talk discusses building the project.
Miriam Posner on

how to get started making a humanities network visualization
using visualization to explore an archive of historical medical photographs (some good research ethics questions here)
"A fun way to introduce DH students to dataviz" lesson
"Getting started with Palladio" ("Palladio, a product of Stanford's Humanities+Design Lab, is a web-based visualization tool for complex humanities data.")

Johanna Drucker's "Humanities Approaches to Visual Display"
Neatline (a platform for telling stories with maps and timelines)
The Gephi dataviz tool (note that you'll probably need to download the 0.8.1beta version instead of the latest; I couldn't get the latest to run on my Mac)
I have several blog posts on introductory use of Gephi for data visualizations on my LiteratureGeek.com blog
"The complete n00b's guide to Gephi"
Scott Weingart on when not to use networks (good for a student discussion on getting past the "prettiness" factor of visualizations)
Ben Fry does a bunch of cool infoviz work, including this timelapse viz of changes in the various editions of Darwin's On the Origin of Species
Ben Schmidt's work, including changing language in State of the Union addresses and whaling routes, visualizing image collections and trends in collections of digitized texts

There's lots of other great visualization, image, and network stuff out there! This was just to blog an email of relevant links I put together after discussing a humanities visualization course that was being designed. Eventually, hoping to combine links like these from various places (Instapaper, Twitter favorites, LibGuides, Zotero) and get them nicely tagged, so pulling out DH work relevant to a project or course being designed isn't entirely based on what I can recall off the top of my head...