Pylon is a compact foundation library for writing portable Eiffel software. It provides the classic data structures (lists, stacks, queue, sets and various tables) with associated access objects like iterators. Other useful clusters provided include: date and time, a simple portable serialisation facility, along with a few other utilities for number formatting and string parsing.
SmartEiffel is the GNU Eiffel Compiler. It is intended to be a complete, though small and very fast, Eiffel compiler. The current distribution includes an Eiffel to C compiler, documentation tools, a pretty printer, and various other tools including an Eiffel debugger. It also includes a large library of classes distributed under the terms of the MIT/X Consortium License. Eiffel is an advanced object-oriented programming language that emphasizes the design and construction of high-quality and reusable software.
SNiFF+ for Eiffel is a 'fuzzy parser' which extends the SNiFF+ development environment for use with the object-oriented language Eiffel. You get syntax highlight in the editor, a class browser, cross reference browsing, and much more. It works independent of your Eiffel compiler and can even cope with source files with syntax errors.