From version 7, VIM has a built in spell check function, but disable by default.
You can use
:set spell and
:set nospell to enable and disable it. The spell check isn’t only for English, use
:echo &spelllang to confirm the current target langurage. Use
:set spelllang=en_GB.UTF-8 to change the target langurage, also you can use
set spelllang=en_us,nl,medical to set it to multiple langurage.