Got an email the other day from blogged.com:
Dear Dr. Matthew,
Our editors recently reviewed your blog and have given it a 7.5 score out of (10) in the recreation category of Blogged.com.
This is quite an achievement!
We evaluated your blog based on the following criteria: Frequency of Updates, Relevance of Content, Site Design, and Writing Style.
I've been a fan of GeoGebra since I saw a demonstration of it by Markus Hohenwarter as MSRI last year. It's a free (open-source), cross-platform (Java-based), dynamical geometry and algebra application.
The nice part about being java-based is you can export your GeoGebra worksheets to html with embedded java applets. And then with a bit of parameter munging you can upload them to your blog. The embedded applet can be as function as the application itself (a nice advantage to being free; it can't be stolen so there's no barrier to making it completely available).
The nice part about being open-source is that people can contribute to it as much as they want. Now in the works is a tool to export a GeoGebra worksheet to PGF/TikZ, so you can put them in your LaTeX documents.
I just discovered that the Library of Congress has established a persistent URL (or "permalink") for every item in their catalog. The data in the link is taken from the item's Library of Congress Control Number (LCCN) and is therefore called an LCCN permalink.