Jaffe, David B.
Whitehead Institute/MIT Center for Genome Research. Computational biology. Coding theory database and links.
Johnson, Bob
UK mathematician providing material on mathematics courses and research including Fibonacci numbers and chaos theory.
Junichi Yananose
Mechanical puzzles and transformable polyhedra.
Juno and her Peacocks
A site about math; graduate and professional life; interesting anmolies; resources and links to things mathematical such as Math Camp.