After quite some time of my thesis (on interactive curve design) being stuck, I'm now making good progress again. You can check out the draft chapter on the history of the elastica if you like (soon also to be published as a Berkeley CS tech report).
I had a lot of fun writing that chapter, digging deep into the history of the curve and getting to know the old mathematicians like James Bernoulli better. My advisor is encouraging me to publish it stand-alone. Can anyone recommend a good place, perhaps some kind of history of mathematics journal or conference?
Next up is a similar chapter on the Euler spiral. Then, after that, I finish up my argument characterizing the entire space of 2-parameter splines, and I'm over the hump - the rest is numerical techniques and applications, which will require making a bunch of figures (time consuming but rewarding), but no difficult conceptual work.
Spiro is integrated with newish builds of Inkscape, which is awesome. Even more awesome is this YouTube video of spiro in action. (The author also has a three minute S using the original ppedit code; nowhere nearly as cool but still nice)
It looks like the word is getting out. There's also a screencast from heathenx. It's still only in development snapshots. I'm excited that when it finally starts shipping in stable releases, lots more people will get excited.
It's also integrated into FontForge, but sadly I haven't gotten much chance to play with it myself. These days, I'm trying to use all my free time on finishing the thesis itself.
You can also see Euler spirals (also known as Cornu spirals or clothoids) at NodeBox, and a nice project by Andren Novali using them. It's awesome that the free software community is carrying this integration work forward even when I have very limited time for coding myself.