https://github.com/makepad/makepad
It's a Rust library for developing cross-platform apps. It's not 1.0 yet; there's still things to finish, but it's being actively developed (https://fosstodon.org/@rikarends#), and it's already pretty fun to play with. And the fact that it compiles and runs with the same widgets on Web as it does for Windows and Mac (Linux and Android are imminent, according to the dev's updates) makes it very appealing for my "write once, deploy anywhere" sensibilities.
Fast, easy, and free. Just waiting on it to be "live", for now! Don't forget to check out the demos.
https://makepad.nl/makepad/examples/fractal_zoom/src/index.h...
https://makepad.nl/makepad/examples/ironfish/src/index.html