Since today is Laetare Sunday, here is the sonnet I wrote last year, based on the Introit and its Psalm (121), plus one verse of Psalm 124. I wish I remembered exactly how I connected the other Psalm to this Introit; but they seem to fit together very nicely. The original Latin is below; the parenthesized phrase is the one I couldn't quite fit into the rhythm/rhyme scheme.

Laetare Ierusalem

Jerusalem, Jerusalem, rejoice!
Let all who love her be united here;
Ye who in sorrow once did lift your voice,
Rejoice, rejoice with gladness and great cheer,

That you be filled from comfort's breast! Be glad,
Jerusalem; her lovers, gathered be;
Ye who before were wretched, weeping, sad,
Exult with merriment and gaiety!

I was made glad by what was said to me,
Into the dwelling of the Lord we go!
And let abundance in your towers be;
Let holy peace be in your strength, also.

O, they who trust in God shall ever be
As Sion's Mount - unmoved eternally.

Laetare Ierusalem: et conventum facite omnes qui diligitis eam: gaudete cum laetitia, qui in tristitia fuistis: ut exsultetis, et satiemini ab uberibus consolationis vestrae.
(Psalm 121) Laetatus sum in his quae dicta sunt mihi: in domum Domini ibimus. Fiat pax in virtute tua, et abundantia in turribus tuis.
(Psalm 124) Qui confidunt in Domino, sicut mons Sion; non commovebitur in aeternum, (qui habitat in Ierusalem.)

Edited to add: the "Fiat pax" and "Qui confidunt" are added to the "Laetatus sum" in the Gradual. (Three cheers for my faithful Liber...)