CMI is an optimizing frontend for gcc which allows gcc to inline across module boundaries without requiring you to put inline functions in header files or even mark inline functions for inlining. It makes your code go faster, makes your code smaller, makes your embedded software use less stack space, is a preprocessor for gcc, supports most gcc extensions, and is able to deal with such notoriously tricky code as the glibc header files. It works by merging multiple C files into one file, topologically sorting the definitions so that definitions come before uses, and marks functions as inline. It controls code bloat by deleting dead code and inlining up until a user-specified budget is reached. You can use user-specified heuristics to select which functions to inline (it includes a tool which uses gprof output to choose inlinings to illustrate this).
DECO (Dynamic Encapsulator of C++ Objects) converts DC++, essentially C++ with extensions for "dynamic encapsulation," into standard C++. Used as-is, DECO can only convert the simplest form of interfaces (types) and implementations to C++, so although it could be interesting, its most practical use is probably to provide a start for parsing C++. Note that template and exception handling support is incomplete in the parser, since DC++ did not make use of these features.
The DObject Library C++ is a Java-like library that acts as a bridge between the C++ and the Java worlds. It offers a wide range of the Java facilities without losing the power of C++. It offers naming convention that is similar to the Java language, smart pointers emulating Java references, and classes emulating Java arrays.
The Database OS (DBOS) is a Java prototype of a high level computing environment. It currently has its own language, compiler (to JVM), and visual debugger It features relational semantics, query ability, a class hierarchy, a source code reflection system, automatic persistence, garbage collection, and an object browser interface.