This is a small add-in for Visual Studio 2008. It searches and highlights substrings that are currently selected in a text editor. As a bonus, it works for Output, Command and Immediate windows too.
Project home: https://github.com/mnasyrov/wordlight
It is pretty simply: when you selects a text, the add-in highlights all occurrences in a current document.
There is a new "Freeze search" feature: you can freeze up to three search results in special mark groups, that stay during text editing. Freezing is called by next hotkeys (by default): Ctrl+`, Ctrl+1 and Ctrl+2 for three groups. For example: you select a text, and all its occurences are marked by pink color automatically. Then you press Ctrl+`, and these marks moved to the blue group. To clear a freezing group just press a hotkey when nothing is selected.
Usually, the folder is placed in "C:\Users\%UserName%\Documents\Visual Studio 2008" (for Win7) or "C:\Documents and Settings\%UserName%\My Documents\Visual Studio 2008\Addins" (for WinXP). It can be checked by "Add-in file paths" settings of the studio (menu Tools > Options > Environment > Add-in/Macros Security).
Please note, the add-in requires installed .NET Framework 3.5 to run.
You can change settings of the add-in by a command "WordLight settings..." under the "Tools" menu.
Tips and tricks
Visual Studio 2008 has various shortcut keys for text search, which look nice with WordLight: