New York - Starbucks at 40th and Lexington - sit in the window and the people-watching is a great way to waste time. (Or Big Cup, on 8th Avenue)

Paris - Cafe Amnesia; La Sancerre, in Montmartre.

Berlin - Cafe Mohring

Chicago - Scenes, on Clark (not sure if that's still there, though). Again, I like the people-watching in that neighborhood.

San Francisco - Cafe di Roma.

Montreal - Presse Cafe on St. Catherine's in the Village, near the metro stop.

EDIT: Scenes hasn't been around for a LONG time -

"In the winter of 1996, nestled in a string of old buildings on Clark Street near Belmont Avenue in Chicago’s Lakeview district, Scenes Cafe closed one evening, bartering away its ragtag collection of furniture and remaining books concerning theater and screen writing. Scenes, owned by two brothers, was forced to shut down due to a Starbucks Coffee House which was opening at the nearby corner in the same stretch of building. Unfortunately for the small, family-owned cafe, the landlords of the buildings had a strict non-compete clause that prevented both cafes from remaining open.1 Due to the immense earning potential combined with the rapid gentrification of the neighborhood, Scenes was left in the wake of Starbuck’s role as symbolic Phallus, simultaneously creating the Law while utilizing the law for its own success.2 The void created by the disappearance of Scenes quickly became mythologized in the minds of former patrons; now abandoned to the streets of Chicago, searching for identification which became only memory, during the times when they would have been sitting in their neighborhood cafe which no longer existed outside of psychological imagery and residual objects which used to occupy a place separate from memory alone. Like Norman Bates in Hitchcock’s Psycho, the patrons of the small cafe had been overwhelmed by the power of the Symbolic Law that had replaced the Imaginary family atmosphere of identification.3 The incestuous link of community had traumatically been fragmented by the algebraic unity of commerce."

http://www.bridgemagazine.org/culture.html