dnGREP - dnGrep allows you to search across files with easy-to-read results.
Capture2text - Capture2Text enables users to quickly OCR a portion of the screen using a keyboard shortcut.
AstroGrep - AstroGrep is A Microsoft Windows GUI File Searching (grep) utility.
TextSniper - Instantly extract any text from your Mac's screen
PowerGREP - Quickly search through large numbers of files on your PC or network using powerful text patterns to find exactly the information you want. Search and replace with plain text or regular expressions to maintain web sites, source code, reports, ...
dpScreenOCR - Program to recognize text on screen