Here are some free add-ins/tools/utilities that you can use in Visual Studio 2005 (or 2008):
Do you use subversion version control system? TortoiseSVN? This add-in is great and integrates very well with all VS versions since 2002.
CLIArgs Made Easy
CLI Args Made Easy (Command Line Arguments Made Easy) is an add-in that allow you to change the command line arguments of the startup project very easily by adding a combobox in the toolbar. It also saves all the arguments you insert for future use.
Microsoft Visual Studio 2005 IDE Enhancements
Set of Visual Studio extensions that improve productivity: Source code outliner, Visual C++ code snippets, indexed find, super diff utility, event toaster utility.
This plug-in allow us to compile the source code files of a Visual Studio 2005 project in parallel. This is extremely useful for processors with more than one core to reduce the compile time.
Power Toys for Visual Studio 2005
Pack with various tools for VS 2005.
Project Line Counter
Reports statistics about the files in projects. It’s automatic, has a filter and you can check its source code.
Refactor! For Visual Studio 2005/2008
Free add-in that refactors (simplifies and re-structures) source code to make it easier to read and less costly to maintain.It has more than 15 different features.
This add-in extends the Visual Studio’s scroll bar showing the code with syntax highlight. It is extremely useful to go to where you want within long source code files.
Free useful gadgets for VS 2005: Editor gadgets – line ruler, indentation guide, auto-copy selection, editor graphic; command spy, file explorer, data object analyzer and SLOC report.
VSFileFinder helps you find files quickly in your projects by typing a few letters from any part of the file name which is much faster than using the solution explorer in large projects.
There is also a version with some improvements (wildcards, regular expressions, personalized tooltips, project filter) and compatible with Visual Studio 2008 available here: VSFileFinder2008.
Visual Studio Add-Ins Every Developer Should Download Now
MSDN page with a collection of free add-ins mostly for .net languages but not only.