For transferring large files between machines that don’t necessarily have the same clients installed I find file.pizza quite convenient.
My understanding is it basically loads a JavaScript BitTorrent client and let’s you transfer using that protocol, so both ends needs to be online, but there is no file size limit, and good support on flaky connections.
There’s a few services like this, but I always find file.pizza to be the one that I remember the name of :)
EDIT: as other people in this thread, I am also having trouble getting file.pizza to work, in both Safari and Chrome.
Maybe it isn’t the answer it used to be.