Windows only: Multiple Find and Replace does pretty much what it says — find and replace text strings across multiple documents. It doesn’t have the binary- and archive-searching power of Windows Grep or the command line elegance of Find and Replace Text for accomplishing tasks, but it is tiny and dead simple. I experience some problems selecting a large range of files, and you’ll probably want to click Show Advanced Options button and select Back up changed files for your first few forays. Multiple Find and Replace is a free download for Windows only.