I had a bit of confusion getting GitX to work from the MacPorts install. I'm documenting it here in case others have the same problem.
I installed GitX from MacPorts. I then typed "gitx" at the command line and saw a "Couldn't connect to app server!" error message. The GitX home page says that you have to run "GitX->Enable Terminal Usage" from the GUI version of GitX before it can be launched from the shell. However, when you install from MacPorts, GitX is not installed in your Applications folder, so it is unclear how to launch the GUI for the first time. The workaround is to find the GitX GUI app in the MacPorts tree. On my machine it is in the /opt/local/var/macports/software/GitX/0.7.1_0/ Applications/MacPorts folder. Launch this app from Finder, and run "GitX->Enable Terminal Usage". Afterwards the gitx command will work from the command line. Hope this saves others a few minutes of confusion.
