I'm a little biased about these first two:
TinyMCE - Add Word-like WYSIWYG Toolbar
Promise - Allows users to commit to do something (like trail care) if x number of other people do it.
User Points - Karma like rating system. Could be used to track volunteer hours.
phpBB - Allow users to log into phpBB with their Drupal username and password.
Volunteer Timeslots Add the ability for users to sign up for particular times. An automatic e-mail reminds volunteers about the upcoming event they've signed up for.
GMap -Add Google map functionality
Simple News - Simplenews is a simple newsletter module which allows both anonymous as well as registered users to subscribe to different newsletters.
Classified Ads - This module creates a simple textual classified ad.
Tasks - Enables a collaborative tasklist
User Badges - The User Badges module allows each user to be assigned 'badges' which can be displayed as a series of iconic images... like trophy for winning a race or icon for trail care leaders, etc
Comments
Mileage Tracker
we have commuters and other groups that would like to log their trips and track their cumulative mileage.
Mike
Trails and Conditions
We currently have a CCK cobbled solution for documenting our trails and conditions but there are some shortcomings in terms of the granularity of providing trail condition information.
Current Solution: http://www.dorba2.com/tmap (be sure to scroll down and see the map with the pins)
Mike
Mike, Love the Location
Mike,
Love the Location integration, but have you thought about building that with Taxonomy or OG so users could get updates using Subscription?
They can get notifications
They can get notifications on updates and comments by content type. But yeah... I need to use taxonomy for at least the trail condition so I can vary the map pins by "open" or "closed". I did the original about 3 weeks into my Drupal adventure.
Mike