RPyC - Remote Python Call, a transparent and symmetric RPC framework for python, which can work either in service-oriented mode or "contract-less" mode, where there's no predefined contract between the two parties. RPyC excels in testing environments, where it enables you to keep the test logic located in a central point, while allowing it to run on multiple systems and platforms.
Construct - Declarative data-structure definition library, where complex constructs can be defined in terms of simpler ones. Since the data structure is declarative rather than procedural, it can be used for both parsing ("unpacking") and building ("packing"), making the library symmetric.
Plumbum - Shell combinators, local and remote command execution, and a programmatic CLI (handling of command-line switches) toolkit
Agnos - The Agnostic RPC framework: a statically-generated cross-language RPC, with support for object proxying
Layer 5 - "The Fifth Layer" of the protocol stack: a network layer that's logically placed on top of layer 4 (TCP) and takes care of negotiations, versioning, reconnects, security, timeouts, etc. -- all in one place, instead of having each application handle it on its own.
Nimp - Nested Imports for python; a small module that enabled the use of java-style namespace-packages; note that similar functionality can be achieved by stdlib modules
sock2 - A pythonic, object-oriented replacement for the
socketmodule, providing much better and consistent APIs. No longer developed.
Conso - Quite a declarative console UI library (e.g. ncurses), in which you build the UI programmatically and the layout happens on its own. Not in a good shape.
Passover - A high-performance python tracer (the tracing part worked great, but I never got to writing a decent trace reader, so it's quite useless this way). Requires Linux (nasty mmap tricks) on x86/64 (uses high-performance a timer).