Starbucks is my always-there, lowest common denominator. There are a lot of little local places in various cities that are really good, but if I don't have a chance to explore, Starbucks will do.

In Buffalo, The Spot.
In Chicago, Intelligentsia or Metropolis.
In San Francisco or anywhere it's present, Peet's.
In Portland, OR, Coffee People.

I haven't found a similar place in NYC - ideas?

Tim Hortons coffee is just hot brown water - like Dunkin Donuts.

edit: Blue Bottle in San Francisco is a league by itself...it's a place for true coffee geeks, with the vacuum-brewed-over-a-halogen-light Japanese thing.