Stanford’s popular free iPhone and iPad apps online course opens June 25 with a new feature: help and inspiration 24×7 via Piazza, a peer-to-peer social learning site — a first for Stanford online courses and on iTunes U.

Whazzit: your questions are answered by course instructors (“course captains”) and by fellow online learners.

When: June 25 to Aug. 27. Registration opens June 19 and ends July 6.

Bonus: The first 1,000 to register may have their own apps — the final project of the course — evaluated for special showcasing on Stanford’s iTunes U site.

Factoid: many students already use the Piazza social learning platform.

Factoid: When Stanford’s first iPhone apps course appeared online in 2009, it made iTunes U history by rocketing to a million downloads in just seven weeks.

Downside: That’s free Piazza, not free pizza.