ShiftIt is a free hotkey based window manager.
Ranked in these QuestionsQuestion Ranking
Pro Easy to configure
ShiftIt is configured through a simple UI where you simply press the hotkeys you wish to map to a certain action.
ShiftIt is very straight-forward to use for most frequent usages.
Pro Open source
Pro Configuration can be committed to your personal dotfiles repository
Configuration winds up living in .hammerspoon/init.lua and .hammerspoon/Spoons/ShiftIt.lua. Very easy to track configuration changes.
Con A little slow
Similar to Spectacle, but it has a few more features, such as being able to pick the size adjustment increments. Spectacle was a little faster, though. Repeated size changes or moves in succession can cause it to wait for it to complete.
Con Imprecise when readjusting sizes
Con Doesn't support moving windows between workspaces
There's no way to move a window to a different workspace with hotkeys in ShiftIt.