This sounds interesting.    The use-cases I hear about most frequently are is situations where there are a lot of "tasks" that need one or more people to fill each task time slot.  Typically these are not connected to any event.  Such as the organizer needs:

5 people at 8am to prepare food

3 people at 10:30 to pack boxes of meals/supplies

10 people who can drive, make deliveries  of food/supplies  to various destinations

etc. 

So the organizer needs a really simple way to set up all the "tasks/needs" at the various times/locations.  I think ease of use/setup needs to be paramount, as the organizer is often NOT a regular user of CiviCRM, and just needs to get their setup of the tasks done very quickly, without needing to be trained in the intricacies of the system. 

Then the people who may be interested in helping need a simple way to see all the options available, and indicate which tasks they want to do.

 An example of a website that is handles this kind of use case nicely is at: http://www.volunteerspot.com

Have you looked at Crew Connect? http://drupal.org/project/om_crew_connect

While this currently isn't tied to CiviCRM, most of the groups already using it are building on http://drupal.org/project/cm_starterkit_moderate which includes the same version of CiviCRM included in http://drupal.org/project/civicrm_starterkit.  

Crew Connect is basically a collection of Profile 2 fields, Views, and some JQuery that turns multiselect form fields into sliders making it much easier to search for a person who's rated themelves or been rated a 3 or higher in a specific skill.  The functionality in Crew Connect is largely Views driven.  The default filter for including a user in a volunteer search is a single checkbox for users to volunteer, but using fields and views you can easily customize this for a variety of use cases.  

Views Send allows users with the approporiate permission to contact each other directly.  

We've already discussed tracking the emails exchanged as CiviCRM Activites.  The skill ratings could also be done as CiviCRM profile fields, but I'd push for the type of syncronization we do w/ http://drupal.org/project/civicrm_multiday_event over only storing the data in CiviCRM.  

A good use case for us is with teams for activities specifically Peer Review. Where people fill out qualifications sheet (check list and open-ended statements) and then are teamed up/ paired together based on skillset and previous work completed.  They are also broken down into distance the reviewer is to the reviewee in hopes of controlling/mitigating travel related expenses/issues.  We have traditionally done this manually but see this module and the Case module overlapping to provide the solution we need. Just some prelim thoughts about our use.

One of the most important features for my organization is the ability to track the number of volunteer hours an individual has contributed.  We use the total number of hours to demonstrate part of our value as an organization.  In addition, we award volunteers with certain benefits at various milestones (100 hours, 250 hours, 1000 hours, etc.). 

Individual volunteers should be able to record their own hours contributed and certain admins should be able to enter hours by event for other individuals.  For example, a regular volunteer would enter their hours each week.  Whereas, for a large volunteer day, one person should be able to enter volunteer hours for a large number of contacts at once.