A Tool for Software Specifications
Try it here: Specr
Specr is tool I've worked on for a while. It's not completely done, but it's good enough at this point to be useable.
Spec'r allows writing specs in outline form. Each part of outline can be explanatory text or can describe a specific software feature.
Features can have requirements - elements of the system that can be precisely defined and tested.
Requirements can have test cases and Spec'r can record test results against test cases.