The
Baal Shem Tov, or Besht — the founder of Chasidism —
met the soul of the Messiah during an ascent to heaven.
The Besht asked him, "When will the Master come?"
The Messiah answered, "When your wellsprings break forth to the outside!"
(from a letter
written by the Besht to his brother-in-law about one of his soul ascents)
A PDF of 44 texts on Tikkun Olam, published in the Journal for Jewish Ethics, which includes indexing by themes, can be downloaded from neohasid.org here.
Texts about tikkun olam make for great text study at your Shavuot tikkun. If you want more Torah resources for Shavuot, click here - including "An Offering in God's Image" about the first fruits, and text study comparing Leonard Cohen's "Hallelujah" with the Talmud and Zohar