Yes, I'm aware of 3rd party spell checkers but I like to have this that's works natively within Opera. Goto GNU Aspell, download and install the "Full Installer" - GNU Aspell-0.50.3 (win32). While your there choose a language pack and install it after you run the Aspell full installer. Close and reopen Opera, now you have a spell check for Opera. Just highlight your text in whatever "field box" your typing in, right click and choose "check spelling". 
