There are in fact more to the Foundation/Robot series than that, actually... the Wikipedia Article on the series has a recommended reading list. A lot of Asimov's stories get tied neatly together in that universe eventually.
However, the ones Ankhani has recommended are the core, and perhaps the best, of it. I'll just add the Empire series
The Stars, Like Dust
The Currents of Space
Pebble in the Sky
to be read in between the Robots and Foundation series. Very good books and a great look at the history of the Galactic Empire.--
"I give you the beautiful... the talented... the tirelessly atomic-powered...
R!
DOROTHY!
WAYNERIGHT!
--
Sucrose Octanitrate.
Proof positive that with sufficient motivation, you can make anything explode.
However, the ones Ankhani has recommended are the core, and perhaps the best, of it. I'll just add the Empire series
The Stars, Like Dust
The Currents of Space
Pebble in the Sky
to be read in between the Robots and Foundation series. Very good books and a great look at the history of the Galactic Empire.--
"I give you the beautiful... the talented... the tirelessly atomic-powered...
R!
DOROTHY!
WAYNERIGHT!
--
Sucrose Octanitrate.
Proof positive that with sufficient motivation, you can make anything explode.