Pattern is a web mining module for the Python programming language.
It bundles tools for data retrieval (Google + Twitter + Wikipedia API, web spider, HTML DOM parser), text analysis (rule-based shallow parser, WordNet interface, syntactical + semantical n-gram search algorithm, tf-idf + cosine similarity + LSA metrics) and data visualization (graph networks).

ScraperWiki is all the tools you need for Screen Scraping, Data Mining & visualisation.

Brewery is a Python framework and collection of tools for analysing and mining data.

The pippi longstrings blog.

A document database that knows the relations between it's documents.

Carrot2 is an Open Source Search Results Clustering Engine. It can automatically organize small collections of documents, e.g. search results, into thematic categories.

An experimental Python console and programmatic framework for building decorated graphs and developing open-source intelligence modules and ideas, centered on social network services, search engines and instant messaging.