Web resources in Mathematics

Being a mathematics graduate I have a passion for mathematics and I am always fascinated by its beauty.Nevertheless I am interested in history of science and mathematics and computer science in particular and whenever I come to know any related web resource I will bookmark that.I discovered Diigo few months ago and it was the kind of tool I was looking for and I moved all my bookmarks from google to Diigo. In addition to just bookmarking it archives the pages bookmarked and it will be helpful if it gets lost in future(and it is very common).Also it is claimed to be a researcher's tool as it has facility to arrange items and highlight information ,share items with others etc.I suggest every one to try Diigo once.Coming back to mathematics I am listing below some links which will be interesting for any maths lover.

1) Wikipedia mathematics portal
Of cource wikipedia is the number one source for any topic.
2) Planet maths
Planet maths is an encyclopaedia for mathematics.It has article on almost every subject and it is reviewed by members. Each topic is owned by one member and so it will be more authentic and accurate.

3)Wolfram Math world and wolfram alpha online
Math world has rich set of details about almost all the branch of mathematics. Wolfram alpha knowledge engine uses mathematica software which helps you to compute so many mathematical functions online quickly.It is a powerful tool for mathematics students and teachers.
4) MacTutor History of Mathematics archive
The MacTutor History of Mathematics archive is the largest source of information in the web about the history of mathematics and also about mathematicians.
5)cut the knot
contains interesting mathematics puzzles and introduction to mathematics topics and problems
6)Springer encyclopaedia of mathematics
Springer encyclopaedia of mathematics acts as a quick reference for mathematics topics available with an index.
7)MIT open courseware
MIT open courseware from MIT is the largest source of learning materials on any subject .
8)Math forum
The Math Forum is a leading center for mathematics and mathematics education on the Internet.It has a lot of resources and links for learning and teaching mathematics.
9)Internet encyclopedia of philosophy
Internet encyclopedia of philosophy has a section about mathematics and logic which is helpful to understand the foundations and philosophy of mathematics.
10)Prime pages
Prime pages has lot of information about prime number research an interesting field in number theory.
11)Gresham college lectures in mathematics
A lot of interesting lectures in mathematics.I found these very interesting and informative.
12)The Math Open Reference Project
A free interactive math textbook on the web. Initially covering high-school geometry.
13)visualmathlearning.com
Understanding Mathematics through Insight, Concept, and Perception
14)math-atlas.org
Introductory articles on almost all the branches of mathematics.
15)NRICH
NRICH is a team of qualified teachers who are also practitioners in RICH mathematical thinking.NRICH aims to Enrich the experience of the mathematics curriculum for all learners.

I hope these links will be useful for all mathematics lovers seeking for resources and reference in web.