Tesseract - Tesseract is an optical character recognition engine for various operating systems
GOCR - GOCR homepage. GOCR is an OCR (Optical Character Recognition) program, developed under the GNU Public License.
Onlineocr.net - Free Online OCR service allows you to convert PDF document to MS Word file, scanned images to editable text formats and extract text from JPEG/TIFF/BMP files
TextGrabber - Office & Productivity
PDFify - PDF creation with text recognition and scanner support. Features email and webpage import to PDF.
VietOCR - A Java/.NET GUI frontend for Tesseract OCR engine.