If your group agrees to a hashtag, then the whole world can easily
follow multiple riders as the event unfolds.  It's super-super cool.
:)

Several of us riding the San Francisco Randonneurs brevet series did
just this.  We used hashtags like #sfr600k and #sfrfleche.  When
stopping to eat and whatnot, I (and other riders) would send a quick
text message to twitter.  Friends and family could easily follow our
progress by looking at our twitter pages or simply the twitter search
page for the event's hashtag.

As a spectator, there are other fun options.  A friend was tweeting a
400k brevet that I was not riding.  I set my twitter account to
temporarily send her tweets straight to my cell phone as text
messages.  As I was out and about doing errands and whatnot that day,
I could see her progress live as she reported it to twitter, since her
updates would come directly to my cell as text messages.  I could also
shoot back replies of encouragement and whatnot.

This doesn't require a fancy cell phone.  My cheap pay-as-you-go cell
phone costs $10 at Target and I pay $20 every three months to keep it
alive.

One annoying thing:  it looks like the twitter search only reaches
back at most a couple of weeks, so I can't send a simple link as an
example any more.  Google helps a bit, though.  For example, try
this...

http://www.google.com/search?q=site:twitter.com+sfr600k

...but click on the "Cached" version of each link -- if you click on
the main link for each result, you'll probably get each person's
current page instead of the slightly-older version cached by Google.
Er this will eventually get purged, too, but it's good at the moment.
;)

If any of you are going to tweet a brevet, please pick a hashtag and
post it here to the Randon list! :)

I'll paste a set of my tweets below as an example.  Newest are at the
top, oldest at the bottom.

-Greg