ACL2 is a mathematical logic, programming language, and mechanical theorem prover based on the applicative subset of Common Lisp. It is an "industrial-strength" version of the NQTHM or Boyer/Moore theorem prover, and has been used for the formal verification of commercial microprocessors, the Java Virtual Machine, interesting algorithms, and so forth.
AI::GA implements a (hopefully) generalized genetic algorithm. It does this by using an array of allowed tokens as individuals. The user has to provide a fitness function. There, the actual representation is implemented. If you have a string of chars, you can simply join them. If you want to have real numbers, you should probably use a bitwise representation and calculate the real values in your fitness function.
AIBash is a project which aims to make Bash act more intelligently. It features typing error-correction and the ability to learn that certain file suffixes are associated with certain programs so that other programs are filtered out while pressing TAB. Other features are planned for the future.
ASpiReNN is a little C library (with Python bindings) which provides support for simple (leaky integrate-and-fire) spiking neural networks. It is primarily designed for highly recurrent networks, but it can also be used with multi-layer nets, though performance won't be the same. Though only Leaky integrate-and-fire (for the neurons) and Spike-Timing Dependent Plasticity (for learning rules) are currently implemented, adding new models shouldn't be too difficult.
The ATRACO Project is a prototype implementation of a trusted ambient ecology system that runs and manages activity spheres in an Ambient Intelligence Space. Activity spheres are realized by automatically discovering, selecting, and adapting smart devices (artefacts) existing in the space, according to user's preferences, customs, and activities. OWL ontologies are used for modeling user profile, devices, activities, and goal descriptions. Abstract plans are bound to specific devices, methods, and values through semantic matching.
AceWiki is a semantic wiki that is powerful and at the same time easy to use. Making use of the controlled natural language ACE, the formal statements of the wiki are shown in a way that looks like natural English. In order to help the users to write correct ACE sentences, AceWiki provides a predictive editor.