Draw.io is open source web-based diagramming software that exports to and imports from a bunch of different formats -- and you can save your diagram as XML so someone else can import and edit it. The info site is Diagrams.net. It has a hilarious footer -- check out the rightmost item, next to "Help and advice" and "About us."

Weightless Books sells DRM-free ebooks. It carries a bunch of indie publishers, and sells back issues and subscriptions for several magazines, such as The Magazine of Fantasy and Science Fiction. And right now, Kaleidoscope: Diverse YA Science Fiction and Fantasy (co-edited by my friend Julia Rios) is on sale from USD $9.25 to USD $4.99. (Weightless Books is run by the same folks as Small Beer Press -- you might recall that Small Beer donated an ebook coupon that we auctioned off at WisCon this year.)

As of a recent version of Thunderbird, you can encrypt and decrypt email with PGP right in the application, without needing the Enigmail add-on! (Background.) This is really useful to me since I use Thunderbird and I work with at least one client who strongly prefers to communicate with me over encrypted channels, including encrypted email.