All the Lois and Clark episodes in which you can see Clark shirtless:

First Season
The Pilot
Pheremone, My Lovely
Honeymoon In Metropolis
All Shook Up
The Foundling
Vatman
The House of Luthor

Second Season
The Church of Metopolis
Metallo
Chi of Steel
Lucky Leon

Third Season
Ordinary People (open shirt, not actually shirtless)
Don't Tug On Superman's Cape
Virtually Destroyed
Never On Sunday
The Dad Who Came In From The Cold
I Now Pronounce You
Double Jeopardy
It's A Small World After All

More soon...