Hunspell - Hunspell is the spell checker of LibreOffice, OpenOffice.
Clipboard Help+Spell - Clipboard Help+Spell is a text-based clipboard utility with the following features:
GNU Aspell - GNU Aspell, usually called just Aspell, is a free software spell checker designed to replace Ispell.
FreeSpell - FreeSpell is a spell checker for any and all Windows applications.
Enchant - The easiest way to scale personalized customer support
ClipMem 3 - Advanced Clipboard-Manager