Thanks for mentioning "Wreck this Journal". It looks amazing!

It reminds me of Brian Eno's venerable "Oblique Strategies": pick a random card and force yourself to follow its instructions. The Oblique Strategies are more targetted at musicians, but are often general enough to be applicable in any situation.

In the same vein, I also liked Naomi Epel's "The Observation Deck", targeted at writers.