TCLink is an LGPL'd thin client API which can run credit card transactions over TCP/IP. A similar package is Red Hat's ccvs, however, it requires that you use a modem or leased line. With TCLink you can run credit card transactions directly over the Internet.
viewportfolio is a python program that allows you to track the performance of a stock portfolio you establish in a data file. It pulls quote information from http://finance.yahoo.com/ and relies on the Quote.py python module written by Jonathan Corbet (included).