Applied Probability Society - A subdivision of the Institute for Operations Research and the Management Sciences (INFORMS) concerned with the application of probability theory to systems that involve random phenomena.

The Applied Probability Trust - The Applied Probability Trust is a non-profit foundation for study and research in the mathematical sciences. It publishes research journals, a student magazine and occasional special volumes.

ArXiv Front: PR Probability Theory - Probability section of the mathematics e-print arXiv

The Collector's Problem and the Two-Dimensional Factorial - In finding a new solution to a classic probability problem concerning the collection of items in a set, a new and useful recursive function has been found, the "two-dimensional factorial."

The Laymans Guide to Probability - An in-depth but easily readable guide on probability theory, covering various aspects of theory with a bias to gambling games.

Math Surprises: An Example - Buffon's Needle simulation and a surprising demonstration of Barbier's theorem about shapes of constant width

Measure and Integration - Part of Dave Rusin's excellent Mathematical Atlas

Parrondo Paradox - Parrondo Paradox simulation and a demonstration of the ratchet effect.

Probabilistic Learning Activities Network - Probability activities and simulations in the form of applets and spreadsheets. This site advocates a Question/Hypothesis/Experiment approach to learning probability.

Probabilistic Thinking - By Richard Jeffrey. HTML.

Probability Guide for Non-mathematicians - Probability theory basics, applications (including to gambling), interpretations, books, free texts.

Probability Theory and Stochastic Processes - Part of Dave Rusin's excellent Mathematical Atlas.

The Probability Web - A collection of pages maintained by Bob Dobrow to serve people with interests in probability theory and its applications.

Theory of Probability - The introduction, formulas, software, algorithms, equations, problems, and calculations.