I thought this was a decent website, but since you asked me, I feel I must tell you, by looking at me, isn't it obvious?
Source(s):
My head! Honest truth!

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Large cloud of swirling gas collapses to form disk and bulge (similar to Solar System)localized collapses form early stars which enrich interstellar medium with heavy elements. Collapse complete, disk formed, spiral arms form, Pop I stars form munching of smaller galaxies occurs. Eventually all gas and dust used up and star formation will cease. A galaxy is a gargantuan collection of stellar and interstellar matter – stars, dust, gas, brown dwarfs, black holes – isolated in space and held together by its own gravity, somewhat similar to islands on a vast sea.
Most of the smudges of light visible through telescopes are not nebulae – clouds of gas and dust – but separate galaxies beyond our own Milky Way. Only long exposure photographs reveal their often intricate structures. The biggest giant elliptical galaxies contain thousands of billions of stars and may be several hundred thousand light years across. Even the tiniest "dwarf" galaxies contain millions of stars. The nearest galaxy, the Andromeda galaxy, is over 2.2 million light-years away. In 1936, Edwin Hubble published a system for galactic labelling. He divided galaxies into four different classes according to their shape. These are spiral (S), barred spiral (SB), elliptical (E) and irregular galaxies.

Spiral galaxies usually consist of two major components: A flat, large disk which often contains a lot of interstellar matter (visible sometimes as reddish diffuse emission nebulae, or as dark dust clouds) and young (open) star clusters and associations, which have emerged from them (recognizable from the blueish light of their hottest, short-living, most massive stars), often arranged in conspicuous and striking spiral patterns and/or bar structures, and an ellipsoidally formed bulge component, consisting of an old stellar population without interstellar matter, and often associated with globular clusters. The young stars in the disk are classified as stellar population I, the old bulge stars as population II. The luminosity and mass relation of these components seem to vary in a wide range, giving rise to a classification scheme. The pattern structures in the disk are most probably transient phenomena only, caused by gravitational interaction with neighboring galaxies.
Source(s):
http://library.thinkquest.org/17445/universe/galaxies.shtml

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