Dunkin definitely. Now having said that, I usually frequent Starbucks for the convenience, sadly it's everywhere.

Dunkin frapps definitely top Starbucks.

For just a simple regular coffee, I actually like 7-Eleven as well.

I go for Caribou Coffee if it's a choice between Caribou and Starbucks.

On the weekends, for just lounging around with coffee and my laptop, I like mom-&-pops coffeehouses...if I can find one. I find most Starbucks to be too loud.