“Spinoza’s formula, “Deus=natura=substantia”, like all conclusions drawn from it in his Ethics and his earlier works, simply means that there is no God. This discovery of Spinoza’s became the starting point for modern philosophical thought.”

Did not appear in Saturday Evening Post story, but quoted in Einstein: His Life and Universe http://books.google.com/books?id=dJMpQagbz_gC&lpg=PP1&pg=PA387#v=onepage&q&f=false by Walter Isaacson, p. 387, in the section discussing Viereck's interview.
1920s, Viereck interview (1929)

Martin Buber, in his Heruth: On Youth and Religion (1919)
A - F

Gilles Deleuze, Expressionism in Philosophy: Spinoza (cited in the Internet Encyclopedia of Philosophy http://www.iep.utm.edu/d/deleuze.htm#SH3b)

Selected works, Spinoza and Buddha: Visions of a Dead God (1933)

Original in German: Ich führe, die Ethik von Spinoza immer bei mir; er hat die Mathematik in die Ethik gebracht, so ich in die Farbenlehre, das heißt: da steht nichts im Hintersatz, was nicht im Vordersatz schon begründet ist.
Johann Wolfgang von Goethe, in a conversation with Boisserée, 3 August 1815. As quoted in Julie D. Prandi's “Dare To Be Happy!”: A Study of Goethe's Ethics (Lanham, MD: University Press of America, 1993)
G - L, Johann Wolfgang von Goethe

Bertrand Russell, in The History of Western Philosophy (1945) Ch. X.
M - R

Friedrich Wilhelm Schelling, On the History of Modern Philosophy (1833) [Translated from the German by Andrew Bowie]
S - Z

Will Durant, beginning with a quote of Sir Frederick Pollock in Life and Philosophy of Spinoza (1899)
A - F

Isaiah Berlin and Ramin Jahanbegloo, Conversations with Isaiah Berlin. (New York: Charles Scribner's Sons, 1991)
A - F