The first prototype of our software can still be downloaded from http://homepages.feis.herts.ac.uk/~comqrb1/ferret.zip, but we are working on an improved version that deals better with a range of input file types (including PDF) and has a rather better user interface. The user interface is illustrated in some screen shots included in a MS Word document.
We hope that the new version will be sufficiently obvious that it can be used without referring to any kind of manual or help file, but for the current version the manual can be downloaded (from http://homepages.feis.herts.ac.uk/~pdgroup/Ferret/FerretManual.zip).
Version 2.1 of Ferret was available here temporarily during the week of the JISC conference where Caroline demonstrated the software. Her Web page has links to some of our publications.
Version 2.2 of Ferret will be available here shortly. Honest!
Version 3 was much better than earlier releases, but only dealt with plain text files.