Perhaps not as graphically compelling as one of my all-time favourite links, the On-Line Encyclopedia
of Integer Sequences sports a spiffy "webcam" for examining sequences in the database.
Spiffy sequence of the day, although with a misnomer:
The Catalan sequence was first described in the 18th century by Leonhard Euler, who was interested in the number of different ways of dividing a polygon into triangles. The sequence is named after Eugène Charles Catalan, who discovered the connection to parenthesized expressions.