I was playing one game a while ago where I found cruise missiles to be EXTREMELY useful. I was basically a large island nation (think Australia) and I deployed loads of cruise missiles along the coast. Whenever an enemy transport/fleet approached, I just lobbed cruise missiles at them until they sank. That way, I could keep the majority of my fleet bombarding the enemy coastline instead of stuck defending the home coast.
I've also found that destroyers can be pretty useful in bombarding an enemy city prior to an amphibious assault. True, the Marines are pretty effective against enemy fortifications, but they're still at a disadvantage (8 attack points versus 10 infantry defense points [baseline]). If you have ten destroyers pelting the city first, that can take a HUGE chunk out of the defensive garrison. Even if the original veteran units are left with two hit points, that's still a big bonus when you're attacking with fresh veteran Marines.
The carriers are also crucial in strategic bombing. The first thing I did -- before attacking anywhere else -- was to knock out the railroads and roads that led to the enemy's rubber squares. Then, on the next turn, they weren't able to draft any infantrymen -- and that makes the job so much easier!
And the moral of this story: bombardment may seem ineffective when you've got only one or two units taking potshots, but an organized campaign can make eventual victory a whole lot less costly in terms of your attacking units.
