Now that QuasarDragon isn't around anymore and since SF Signal only indexes Manybooks texts, here's the latest public domain Golden Age sf from Project Gutenberg.
The Adventurer by C. M. Kornbluth (Space Science Fiction, May 1953)
"For every evil under the sun, there's an answer. It may be a simple, direct answer; it may be one that takes years, and seems unrelated to the problem. But there's an answer—of a kind...."
The Second Voice by Mann Rubin (Fantastic Universe, March 1954)
"Spud, world-famous dummy, talks to Mars with surprising results."