Sunset (GitHub: amdt / sunset, License: Vim) by Alastair Touw automatically sets
background when the sun rises and sets. It works with themes that have light and dark variants, and Alastair points out both Solarized and Hemisu support this.
Makeshift (GitHub: johnsyweb / vim-makeshift, License: Vim) by Pete Johns detects which build system
:make should use by setting
'makeprg' based on the files present in the working directory. The built-in build systems are Make, Rake, SCons, Ant, Maven, CMake, and BJam, but more can be added by setting