Hawth's Analysis Tools is an extension for ESRI's ArcGIS (specifically ArcMap). It is designed to perform spatial analysis and functions that cannot be conveniently accomplished with out-of-the-box ArcGIS.
Most of these analysis tools have been written within the context of the ecological applications I am involved in (movement analysis, resource selection, predator prey interactions and trophic cascades). However, they have been created in such a way as to be as broadly applicable as possible such that I hope people from many disciplines will find use in this set of tools.
There are three types of tools in this kit. First, there are simple tools that automate mundane tasks (e.g. deleting many fields at once from a table). These will likely be useful to anyone.
Second, there are tools that are designed to be part of an analysis workflow. For instance, random point (or stratified random point) generation, minimum convex polygon delineation, summarizing raster layers in various ways, etc. These too are likely to be useful to many people.
Finally, there are tools that target specific, ecology related analyses (for instance, various movement model applications). These will likely only be of interest to ecologists.
Specific detail of the tools can be found on the Tools page.
Hawth's Tools is FREE. You are free to distribute it and install it anywhere you choose. As there are continual updates and additions to the tools, it is recommended that you check this website from time to time for more recent versions.
I am always happy to hear constructive suggestions and comments about these tools.