Bug Magnet is an open source Chrome extension that provides an easy access to common software testing problematic values and edge cases. You will be able to access them easily during exploratory testing sessions so that you can fill the tested fields with a chosen value. A Firefox equivalent has also been developed.
SST or Selenium Simple Test is an open source web test framework that uses Python to generate functional browser-based tests. The tests are made up of scripts, created by composing actions that drive a browser and assert conditions. You enjoy the flexibility of the full Python language, along with a convenient set of functions to simplify web testing, but the commands are simple and flexible enough that the tool can also be used by non-programmers.