The VoxSpell plugin checks the spelling of English language documents while you are typing, underlining the mispelled words whenever they are found.
More languages may be supported in the future, contact the author if
willing to help.
It comes bundled with an English language dictionary
produced from the SCOWL word list hosted at (Kevin's Word List Page).
Warning: the algorithm used to store the word suggestion list is unoptimized. This plugin consumes, typically, ~30MB of memory