Other
University of Tennessee: The Prime Pages
Here you can find a detailed searchable database of the 5000 largest known primes! Content also includes a glossary, a top 10 records list, prime-music, programs, free downloads, and much more!
Ministry of Education and Universities of the Region of Murcia (Spain)
Ministerio De Educacion Y Ciencia: Numeros Primos
This interactive unit explain what prime numbers are and how to find them. It also discuss the Sieve of Eratosthenes and the Mersenne number.