When I was a student at The Master's University (then still The Master's College), my Old Testament Survey II professor was Dr. William Varner. In his note packet for the class he had these couplets written out to help us remember what each minor prophet was about. (He even gave us extra credit on the final if we wrote them out on the back page!). I can't find them anywhere else on the internet, so I'm putting them here so that perhaps they will come up if someone else is trying to dig them up.
Hosea
Hosea pictures faithful love
To man below from God above.
Joel
In Joel locusts strip the land
And then comes judgement from God's hand.
Amos
The plumbline shows in Amos' book
The grim result when God's forsook.
Obadiah
The prophet Obadiah cried
For God to deal with Edom's pride.
Jonah
In Jonah's book a fish is sent
To help the prophet preach 'Repent!'
Micah
In Micah's book Messiah's birth
Brings hope for justice on the earth.
Nahum
In Nahum's book a stronghold's found
That keeps the saint both safe and sound.
Habakkuk
Habakkuk's prayer brings this reply:
"The just shall live by faith on high."
Zephaniah
In Zephaniah lukewarm love
Results in judgement from above
Haggai
A half-built temple spells disgrace
Till Haggai thunders, "Build with haste."
Zechariah
In Zechariah's nightly dreams
God gives us Messianic themes
Malachi
In Malachi the nation's sin
Prevents God's truth from entering in.