To list installed packages:

$ pip list
# example output
docutils (0.9.1)
Jinja2 (2.6)
Pygments (1.5)
Sphinx (1.1.2)

To list outdated packages, and show the latest version available:

$ pip list --outdated
# example output
docutils (Current: 0.9.1 Latest: 0.10)
Sphinx (Current: 1.1.2 Latest: 1.1.3)