Tesseract: fast n-dimensional filtering and grouping of records in the browser:

D3.js is a small, free JavaScript library for manipulating documents based on data.

csvkit is a suite of utilities for converting to and working with CSV, the king of tabular file formats.

Takes CSV or tab-delimited data from Excel and converts it into several web-friendly formats, include JSON and XML.

Tangle is a JavaScript library for creating reactive documents. Your readers can interactively explore possibilities, play with parameters, and see the document update immediately. Tangle is super-simple and easy to learn.

Crazy set of talk slides from Mike, really beautiful

d3.js is a data visualization library by Mike Bostock, who is also the primary creator of Protovis, which D3 is designed to replace.

Historical weather data

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

Tablib is an MIT Licensed format-agnostic tabular dataset library, written in Python. It allows you to import, export, and manipulate tabular data sets. Advanced features include, segregation, dynamic columns, tags & filtering, and seamless format import & export.

Sometimes you just need some data to test and stress things. But randomly generated data is awful — it doesn’t have realistic distributions, and it isn’t easy to understand whether your results are meaningful and correct. Real or quasi-real data is best. Whether you’re looking for a couple of megabytes or many terabytes, the following sources of data might help you benchmark and test under more realistic conditions.

Barnum is a small application that can be used to create pseudo-realistic data suitable for unit or performance testing.

The Data Conversion Handbook, edited by Walt Kester (Newnes, 2005), is written for design engineers who routinely use data converters and related circuitry.