Linux (ubuntu) using xfce. Always have one workspace devoted to a full-screen Vim window, so can get there with a keyboard shortcut. In my .vimrc, I have

    set clipboard=unnamedplus

so that yanked text is copied to the X11 clipboard. Yank buffer, switch back to browser (or what have you), paste. With Vimium, the whole procedure is mouseless.

pbcopy on Mac brings back memories.