What font does Basecamp use? The closest font you can get for the Basecamp logo is Interstate Regular…
What font does 37signals use? The closest font you can get for the 37signals logo is Interstate Bold font.
Designers: Tobias Frere-Jones
Free alternative fonts for 37signals logo:
The closest free font you can get is Blue Highway Font.
About free fonts:
Fonts by Ray Larabie