I have this in my controller.py (or any other module I wish to interactively inspect/debug):
from IPython.Shell import IPShellEmbed
dbg = IPShellEmbed()
...
class Root(controllers.Root):
@turbogears.expose(html="app.templates.method")
def method(self):
dbg() # this will put your server into interactive mode which
can be exited with Ctrl-D
You must install IPython (http://ipython.scipy.org/) for this to work.

