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.
TextGrabber - Office & Productivity
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
CopyFish - Copy, paste and translate text from any image, video or PDF.
VietOCR - A Java/.NET GUI frontend for Tesseract OCR engine.