I love rotating insoles around to different shoes. Especially when I find brand X has a removable insole that I enjoy. I'll keep them until they're dust usually. My favorites are Etnies STI, State Footwear, and Emerica G6 insoles.
They allow you to break in new shoes quicker (fit and comfort is usually better) and squeeze a few drops out of some shoes that usually would be ready to trash like MBrimson said.
Here's a list of insoles I've used from brands that last long enough to move from shoe to shoe in no particular order:
Es: Energy Foam
Nike SB/Cons: React, Lunarlon, Zoom Air
Etnies: STI Pro Foam
Emerica: G6 (removable insole, only present on their G6 vulc models)
State Footwear: standard vulc insole
Vans: Ultracush, Popcush, Ultracush 3D
Alternatives I've either not tried or tried with less than stellar success
Lakai: DeluxLite/LuxLite
Hours is Yours: Goddess insoles (the newest ones)
Globe: Nitrolite, Lux Shockbed
Last Resort AB: Cloudy Cush (the new revised ones)
It is funny with some shoes, at least trying on way too many shoes in skate shops or where I used to work, just to see what they are like, but I definitely could have used some of the insoles from various shoes over the years, way more than the shoes themselves.
What insoles were in the Koston shoes, cause they were amazingly thick and sponge like??? Maybe twice as thick as the other lunarlon insoles in Cons and Nike shoes, but in the same colour.
The G6 insoles are another one that come to mind, that were easily accessible with lots of shoes on clearance so it was almost cheaper just to buy the shoes for the insoles and give away the shoes with something else in them.
Both of those I never did go through with it, but it always interests me to pull out insoles and check / compare them.
Most recently the Last Resort looked pretty good, much like the Huf and Gravis insoles from way back when, but also the Habitat and Diamond shoes, which all resembled the first version of the Vans insoles, the thicker rubber feel material before popcush or ultracush or any of the ones out now.