Teambox-Client is a project mainly written in Python, it's free.
Python client for team box API
from teambox import Project
project_api = Project(username="username", password="password")
# Or if you have your inhouse installation of teambox
# project_api = Project(
# base_url="https://my-inhouse-teambox.com",
# username="username", password="password")
# List all projects
project_api.index()
The documentation with source code is hosted on github at http://openlabs.github.com/Teambox-Client/