Tesseract - Tesseract is an optical character recognition engine for various operating systems
Capture2text - Capture2Text enables users to quickly OCR a portion of the screen using a keyboard shortcut.
PrimeOCR - PrimeOCR is listed among the leading OCR.
TextSniper - Instantly extract any text from your Mac's screen
PDF OCR X - PDF OCR X is a simple drag-and-drop utility for Mac OS X and Windows that converts your PDFs and photos into textual content files or editable PDF documents.
dpScreenOCR - Program to recognize text on screen