Here are all the cheats from the Blizzard website:
Show me the money - Gives you 10,000 gas and 10,000 crystal
Operation CWAL - Speeds construction of buildings and units
The Gathering - Gives unlimited energy to all casting units
Game over man - Ends your game as a loss
Staying Alive - Prevents the mission from ending due to victory or defeat
There is no cow level - Completes the current mission
Whats mine is mine - Free minerals
Breathe deep - Free Vespene Gas
Something for nothing - Gives all upgrades
Black Sheep Wall - Shows entire map
Medieval man - Free upgrades to units
Modify the phase variance - Ability to build all buildings
War aint what it used to be - Disables fog of war
Food for thought - Ability to build units beyond the support limit
Ophelia - Enter this to enable level skipping cheat. Then enter the mission you want to skip to (i.e., "terran10") to go there. For Brood War levels type x before the levels (i.e., "xterran8")
Radio Free Zerg - Brood War cheat for hidden Zerg Song. Must play as Zerg when using Cheat.