Adobe Systems: All major applications are developed in C++:
Photoshop & ImageReady,
Illustrator,
Acrobat,
InDesign,
GoLive,
Frame (mostly C, some C++)
Alias|Wavefront: Maya. Maya has been used in the production of just about every major film involving computer-generated effects since its release, including Star Wars Episode I, Spider-Man, Lord of the Rings, Stuart Little, etc. "I love 3d animation".
Apple: OS X is written in a mix of language, but a few important parts are C++. The two most interesting are
Finder
IOKit device drivers. (IOKit is the only place where we use C++ in the kernel, though.)
Also,
AppleWorks
the iPod user interface (uses Pixo application framework written in C++)
"Of the thousands of Macintosh applications that have shipped I estimate that over half were written C++".
Frameworks: There are three major C++ application frame works developed for Macintosh: Apple's MacApp (some MacApp applications), Symantec's Think Class Libraries, and Metrowerks' PowerPlant. There are also a number of smaller (in market share) frameworks that have been developed.
Google: web search engine, etc.
HP: Here is a tiny fraction of HP's C++ apps:
C, C++, Fortran90 compilers, and linker for the new HP IA64 platform (these add to morethan 1 million lines of C++ code).
SAM (HP's system management utility)
Some of the networking libraries in HP-UX
Java VM core
Parts of Openview
Non-stop XML parser (originally from compaq)
IBM: OS/400.
Mentor Graphics: Since the 1980s Mentor Graphics has built most of its applications using C++, including:
Calibre: software for IC physical verification, manufacturing, and resolution enhancement.
Formal Pro: formal verification equivalency checker which enables multi-million gate ASIC and SoC verification.
FastScan: automatic test pattern generation tool for ASICs and ICs.
FlexTest: test pattern generation for optimizing test coverage.
TestKompress: tool suite which reduces ATE memory and time requirements for testing by up to 10 times.
MachTA/PA: fast, accurate, high capacity, transistor-level circuit simulation for timing and power analysis of DSM and mixed-signal IC designs.
Microsoft: Literally everything at Microsoft is built using various flavors of Visual C++ - mostly 6.0 and 7.0 but we do have a few holdouts still using 5.0 :-( and some products like Windows XP use more recent builds of the compiler. The list would include major products like:
Windows XP
Windows NT (NT4 and 2000)
Windows 9x (95, 98, Me)
Microsoft Office (Word, Excel, Access, PowerPoint, Outlook)
Internet Explorer (including Outlook Express)
Visual Studio (Visual C++, Visual Basic, Visual FoxPro) (Some parts of Visual Studio like the Base Class Libraries that ship with the .NET Framework were written using C# but the C# compiler itself is written in C++.)
Exchange
SQL
There are also "minor" products like:
FrontPage
Money
Picture It
Project
and all the games.