A number of people saw the debugging Django post and suggested I'd write one covering TurboGears as well. Great idea, so here goes...

I found the best approach for this was to use the remote debugging method:

• Edit your TurboGears main file start file "start-projname.py" and
  add the following lines, ensuring they are the first 2 code lines in the file:
  import dbgp.client
  dbgp.client.brk(host="localhost", port=9000)

  Note: Change "localhost" to be the machine Komodo is running on (it can be on a different machine) and change 9000 to be the debug port Komodo is set to listen to, you can find this debugger port by looking at Komodo's menu "Debug->Listener Status".

  This ensures that Komodo's dbgp debugging client gets properly initialized and any subsequent threads will get properly debugged by Komodo.

• Add breakpoints to your python code like this:
  
  from dbgp.client import brk # Import Komodo debugger brk function
  import time
  from turbogears import controllers, expose, flash

  class Root(controllers.RootController):
      @expose(template="todd1.templates.welcome")
      def index(self):
          brk()    # Make Komodo debugging break here
          return dict(now=time.ctime())

• Ensure Komodo's python dbgp is on your pythonpath, and then start your server:
  export PYTHONPATH=/path-to-komodo-install/lib/support/dbgp/pythonlib
  Note: Change "path-to-komodo-install" to be you Komodo install location.
• Run your TurboGears server:
  python start-projname.py

Some notes on TurboGears and autoreload:

• If you are using the auto-reload feature (you likely are as it's turned on by default in the dev version), you'll initially get 2 debug sessions connect to Komodo. The first is for the reloader and the subsequent one(s) are for the server.
• I say subsequent one(s) because everytime you change a controller file, the server will reload, it does this by shutting down the old process and creating a new process, so this initiates a new debug session to Komodo!
• For debugging purposes, I suggest turning off this auto-reload functionality by setting the following in your TurboGears config file (i.e. dev.cfg):
  autoreload.on=False