[Dec 09] HawthsTools is now formally discontinued. The new software that replaces and improves upon Hawthstools is called the Geospatial Modelling Environment.
[Sept 09] HawthsTools has not been updated for a considerable time and is soon to be formally discontinued. It will be replaced with an entirely new software package that has much greater functionality. Issues have been found when using these tools with recent versions of ArcGIS and I recommend that you cease to use HawthsTools. These problems arise because the ArcGIS programming interface (ArcObjects) tends to change with each update of ArcGIS. This is particularly true for major releases. This breaks backward compatibility, and means that bugs can be introduced into tools that were compiled against a previous version of ArcGIS. Of course this creates a great deal of work for developers who have to constantly keep up with changes in the object model and the lack of backwards compatibility - a highly unsatisfactory state of affairs. I suggest you watch www.spatialecology.com for details of the new product, due for release before the end of the year.
Links to full descriptions and help files:
Important: these tools do not currently support on-the-fly projection changes, therefore for any of the tools that work with more than one layer, you must ensure that they share the same projection.
Note that this list of tools and the associated help files applies to the most
recent version of HawthsTools (for ArcGIS 9). Development of the ArcGIS 8.x version of HawthsTools has stopped because of the difficulties of maintaining two incompatable code bases.