SprySpell for plain text:
Type (or paste) any text that you wish to spell check into the above box and click the spell check button. The text will then be checked by SprySpell and misspelt words will be highlighted allowing you to select a replacement from the list which pops up when you run the mouse over the word. You can then click the "correct spelling" button and SprySpell will make the changes to your text for you. The corrected text can then be copied into whatever application you wish.