Here are some interesting links..
Dilbert.com
PhD Comics
Calvin and Hobbes
GGobi : Interactive data visualization and more!
South Asian Studies@Penn : Events related to India at UPenn, check the great concerts!
Sruti : India Classical Music and Dance society for the greater Delaware valley
Painted Bride Art Center : Philly's hippest center for the contemporary arts.
Philadelphia Museum of Art
Web Museum : Has quite a few artworks online..
The Curtis Institute of Music
Penn Presents
The Classical Music pages : Everything you wanted to know but were afraid to ask about classical music :)
somaweb.org : who else?
Becoming Human : Paleoanthropology, Evolution and Human Origins