Add dialog Spell checking to your Silverlight applications (SL v3, v4 and Windows Phone 7). Supports plain text boxes, rich text boxes (SL v4) and 3rd party controls. Designed to have a Minimal foot-print, uncompressed, the DLL and English dictionary total only 570KB.
Features:
Supports SL 4 RichTextBox
Open API
Very Customizable
Multiple Languages Supported (Dictionary & UI)