Exceptionally interesting and useful links

Judaism [mostly in Hebrew]

Shiduchim: Free dating Gmahs for Jews.
Judaism in flash: Start with this one.
Manof: The center for Jewish Information. Read, react, learn and enjoy.
Online books: A comprehensive index and links to many online books in Jewish law and thought.
The advantages of orthodox education: A scientific research proved orthodox students have better mathematical intuition!
Temple Institute: Has some beautiful drawings of the temple.
Machon Mamre: The Tana"ch + Mishne Tora + other basic books, including Nikud (vowels). Also includes the famous MTR freeware for search in Jewish texts.
Free coupons: Coupons for Kosher restaurants in Israel. You can search for your preferred restaurant there!
The inner dimension: Lectures on Chassidut, Torah and Science, and beautiful Melodies, of Rabbi Ginsburgh, a major Haba"d Rabbi.
The magician: A tale for adults, with a charming backgroung music by Rabbi Ashlag.
Lashon Ha'ra: A cute story demonstrating what this is.
Daat: Almost everything about Judaism - articles, lectures, books, and more.
Basic sacred books: A database of Torah, Mishna, Talmud and more, with searching tools.
Mathematics in Jewish sources: This is my and David Garber's site on the subjects. See also this site.
Orthodox fiction: Rachel Pomerantz' Home Page on Jewish orthodox fiction.
Radio 10: A voluntarial-basis Jewish radiostation which is chased by the government (which turns it down from time to time). It is far, far more professinal than the other religious radiostations, and I often listen to it when it is up.
Films: Online (clean) short films related to Israel, Judaism, etc.
Codes in the Bible: Search engines (free), discussions, and links.
E-daf: The Babylonian Talmud scanned. Excellent for Daf Yomi when you're abroad.
Ask The Rabbi: Various Judaism sites, including links to many sites where you can email questions to Rabbi's in all branches of Judaism.
Tzura: A relatively kosher literary site -- publish there!
The Jewish Encyclopedia: Online, free.
Sources from BeSheva: A summary of links from an article which appeared in Besheva newspaper.

Or-Shalom: An internet site dedicated to the heritage of the Tripolitan/Lybian Jewish community, a community which is said to have existed since the days of the first temple, and almost completely immigranted to Israel as soon as it could (mostly in 1945--1950, I think).
Tsurba Merabanan: Halach studies through sources.

LateX stuff

A not so short introduction to LaTeX2e: Learn almost everything you need to know about the LaTeX scientific word processor in less than two hours!
DeTeXify: Freely draw a symbol to get it's latex abbreviation.
LaTeX manuals: Contains some online manuals for LaTeX.
LaTeX, including Hebrew, for Windows: Install everything as instructed there, and then install WinEdt. Together, you get the best combination I know of LaTeX and Hebrew (the Hebrew text is written from left to write in the editor, but it is easy to get used to that.)
TTF with TeX: How to use true-type fonts with TeX. Some hackers (that is, Mishael Sklarz) know how to use this to use HEBREW TTF's with TeX, now THIS is important, since Hebrew TeX's default fonts are a sad story which you do not want to read... One day I'll force Misha to write a web page how to do this.

Translators and converters

Babel Fish: Translates text and HTML pages between various (human) languages. Amazing!
PC2LaTeX: Converters from PC editors to LaTeX, and links to other converters.
TTH: Convert from TeX/LaTeX to HTML, also converts formulas to regular HTML!
Rav-Milim: Yaacov Chouweika's dictionary online, with many additional features.
The free dictionary: English-English dictionary.

Search engines

Google: The best search engine I know. (Rates sites according to the number of links pointing to them.) Can find the homepage of a person by his name.
Scopus: Try it.
Scirus: Searches in scientific information only.
MathScinet: Search for papers in mathematics and their reviews (AMS).
Zentralblatt MATH: Search for papers in mathematics and their reviews (EMS).
JSTOR: Search and retrieve papers in several journals.
CiteBase: Tells the number of hits and citations your paper got in the Math ArXiv.

Mathematics

Selection Principles in Mathematics

This is my field of research (truly fascinating!). In addition to my papers in this field, which are available here, the SPM team is building an internet site which will grow to contain everything under the sun which was done in this field.
Sequences: Look for your favorite sequence.

Encyclopedia

Wolfram's online Encyclopedia of Mathematics


wwElsevier

Elsevier's neat site containing top articles and math news.


Linear Algebra

Summaries and online exercises: If you are my student you may find this useful.


Free books in mathematics

E-brary: Search and view many online books on almost any subject.
Hebrew math books: for free Hebrew books in Mathematics. Please let me know of any other interesting free books on the www.
Haifa University online books list.
Geometry and Topology Monographs.
AMS books.
Herebert Wilf's books: Including: Generatingfunctionology, and A=B.
George Cain's online books page: A large collection of (links to) online books in mathematics and CS, including Handbook of Applied Cryptography.
More online books: Containing links to books and other "free books" sites.
Journals of interest: Various journals you may wish to know about (under construction).

Online free journals

Saharon Shelah's archive: All titles (almost 800 now) of the phenomenal mathematician Saharon Shelah. This is probably the best place to look for new results in set theory and related fields.
Geometry and Topology
Algebraic and Geometric Topology
Documenta Mathematica
Forum Geometricorum

HTML and internet (free) stuff

FastCounter: A visit counter by LinkExchange
Site Meter: Another visit counter.

Miscelenaous

Applied Cryptography: Bruce Schneier's excellent book online.
Makor Rishon: A reasonable Israeli newspaper (one which you can read without regretting it).
Hevre: Find your old friends, send them emails, etc.