These are events when git developers (and in one case, one user) physically meet in the same place.
2 GitTogether took place in 2009:
October 26(Mon)-28(Wed) in Mountain View, California
For further details, see the GitTogether09 planning page.
"Alles Wird Git" Berlin GitTogether '09
GitTogether08 took place October 27-29 2008 in Mountain View, California, with around 25 developers and users.
One such event happened in 2007 with a few developers. It was an informal, fun time, but not technical.