Openoffice (Windows) comes with a Shell Extension that allows document 
properties to be accessed from outside OO.

This has several usefull uses:
-Some properties can be browsed from Explorer
-Explorer can display a preview of the document, espcially Signed documents 
show a "stamp" on signed documents
-Indexing services have access to keywords, document title etc.

The document properties can also be displayed in the Detailed view of explorer.
Normally this view only shows filename, date, size etc. However Explorer allows 
to add additional properties to this view. This allows the user to sort 
documents by the "internal" document title or other exposed properties.

A usefull feature would be to show also names and dates of the users that 
signed the document. This allows to quickly see if all needed signature have 
been placed on documents.

Moreover, currently when documents have been signed by multiple users, OO's 
internal save date becomes the date the first user signed the document. for 
unsigned documents the file system date is used. This causes inconsistancy 
between file system date and the date shown in the document.

Proposed behavior:
a property Signed On (the date of the first signature)
a property Signed By (the names of all the users that put a signture on it).

Our application:
We have written an app that uses the Shell Extensions to Extract Author, 
Filename, Title, Keywords and date.
This quickly creates a html document with links to all the documents in a 
folder and its sub-folders and the relavant properties.

Right now it shows (incorrectly) the file system date, which is diffent from 
the Changed Date field shown on printed documents.

This tools is internally used for registering documents as required by QA 
systems like ISO9000. We believe such functionality will benefit others 
considering electronically signed documents as well.