PrimePages
The Prime pages is a website about prime numbers maintained by Prof. Chris Caldwell at the University of Tennessee at Martin. Hobbyist efforts to find large primes are co-ordinated at this site. The list of the "5000 largest known primes" and lists of "top twenty" largest known primes of various interesting forms are maintained here. The site has a wealth of articles on primes and primality proving. Recent additions include the "Prime Glossary" and "Prime Curios" sections.