Other Platforms of Life

Imaginary but possible lifeforms on a jupiter-like planet. Photo from page 42 of Carl Sagan's Cosmos.

A post at io9 mentions the possibility of life aside from the usual carbon-based or water-based type.
I'm reminded of the musings and calculations of the late Carl Sagan (with his colleague E. E. Salpeter) regarding the form of life that may arise from a Jupiter-like planet. They would look like gigantic Jellyfish basked in gasses (such as ammonia and methane) that may be poisonous to us, but is the basis of their very life.
Because life that happens to sprout in a certain environment thrives off the available "resources" that happen to be there. We've seen it in extremophiles on our very own planet. It may very well be the case elsewhere.
With the multitude of combinations of different properties of stars and exoplanets (such as mass, temperature, chemical make-up) the possibilities and variety of life across the universe might be endless and may be totally anything we could ever imagine.

Habitable Zone: Starting from Home

We had to start somewhere. In trying to determine where life might likely arise in other parts of the universe, a guide and yardstick had to be set. Where else should we begin with but home? Such is what i think is behind the concept of the Habitable Zone (HZ), a region of space where conditions are favorable for life as it may be found on Earth. More specifically, HZ is a region around a star in which water can exist in liquid form.
Its very anthropomorphic, I know, and is constrained for water-based and carbon-based lifeforms, but it's a very good start in the search for exoplanets and life in deep space.
Probabilities and the likelihood of finding life in other places begins with Earth as the model and guide, hinging on Water. Planetary missions, such as the Mars Exploration are on the lookout for signs of water. Because water means life, er to begin with.
Slowly but surely, we are now expanding our sphere of thought from the basic Habitable Zone concept to other worlds. From Mars, Jupiter and its moon Europa, all the way to an exoplanet called Gliese 581c. Soon there will be more worlds to think about. And more platforms of life to speculate on, not just carbon, but perhaps methane.
And the day will come when a variety of Habitable Zones will be identified, not just the traditional Earth-like or water-based kind that we know of.
When we finally find signs of life or life itself on a distant exoplanet, we will remember the day when the concept of the most basic Habitable Zone was formulated...hey, we had to start somewhere.