A very simple tool for transferring files between two computers. Linux <-> Windows should just work, uPnP handling, etc - just a crazy simple way to transfer a file without setting up Dropbox, ftp servers or whatnot!
People usually recommend https://file.pizza but it just doesn't work for me.
Now that I think about this it would be beautiful if there was something like stunnel but for NAT hole punching and what not. You would do:
$ send-file FILE
qk11c14pmq7maeod
$
I just use good old SMB/network sharing - it's not much harder than setting up some program on two devices. Works between Windows/Linux/Android, fast and good enough.