Puzzles sites

1.- Frank Rubin Contest Center
2.-  Macalester College POTW
3.- Lloyd King's, Aha! Puzzles
4. Uncle Bob's Puzzle Corner
5. Ed Pegg, Jr. MathPuzzle pages.
6.- Claudio Meller's site

Number patterns

1.- Patrick De Geest, World of Numbers  
2.- Magic Stars and other patterns by Harvey Heinz
3. Shyam Sunder Gupta's Number recreations
4. Mutsumi Suzuki, Magic Squares.

General references

1.- The Chris Caldwell Site
2.- Eric Weisstein’s MathWorld Encyclopedia  
3.- On-Line Encyclopedia of integer sequences , by Neil s. Sloane.
4.- Prime Curios!, by G. L. Honaker, Jr. & Chris Caldwell     
5.- Smarandache's works about primes
6.- John Cosgrave pages about several primes issues
7.- Mudd Math Fun Facts pages
8.- Open Directory, Number theory

Codes for primes

1.- Proth.exe, by Yves Gallot. For the GFN search click here. 
2.- Fermat.exe for hunting small Fermat's prime factors, by Leonid Durman
3. Mersenne primes search by GIMPS

On Line applets

1. Factorization:
a) Jack Brennen
b) Factoris, by XIAO Gang
c) ECM by Dario Alpern

2. Primality:
a) The Nth prime page
b) Germany
c) Primes by XIAO Gang
d) Caltech

3. The number Empire (Factorization, Primality & others) by Vitalii Vanovschi.

Others Pages

1.- José Espinoza, Induction and Number Theory site

FAQ pages

1.- This site FAQ Page
2.- Chris Caldwell's Frequently Asked Questions about Primes
3.- Ask Dr Math's FAQ Page about many mathematic issue.
4. Looking for lost web pages? Use this link.