Category	Style
1. Light Lager	Light American Lager, Standard American Lager, Premium American Lager, Munich Helles, Dortmunder Export
2. Pilsner	German Pilsner, Boehmian Pilsner, Classic American Pilsner
3. European Amber Lager	Vienna Lager, Oktoberfest/Maerzen
4. Dark Lager	Dark American Lager, Munich Dunkel, Schwarzbier (Black Beer)
5. Bock	Maibock/Helles Bock, Traditional Bock, Doppelbock, Eisbock
6. Light Hybrid Beer	Cream Ale, Blonde Ale, Kolsch, American Wheat or Rye
7. Amber Hybrid Beer	Northern German Altbier, California Common Beer, Dusseldorf Altbier
8. English Pale Ale	Standard/Ordinary Bitter, Special/Best/Premium Bitter, Extra Special/Strong Bitter
9. Scottish and Irish Ales	Scottish Light 60/-, Scottish Heavy 70/-, Scottish Export 80/-, Irish Red Ale, Strong Scotch Ale
10. American Ale	American Pale Ale, American Amber Ale, American Brown Ale
11. English Brown Ale	Mild, Southern English Brown, Northern English Brown Ale
12. Porter	Brown Porter, Robust Porter, Baltic Porter
13. Stout	Dry Stout, Sweet Stout, Oatmeal Stout, Foreign Extra Stout, American Stout, Russian Imperial Stout
14. India Pale Ale	English IPA, American IPA, Imperial IPA
15. German Wheat and Rye Beer	Weizen/Weissbier, Dunkelweizen, Weizenbock, Roggenbier
16. Belgian and French Ale	Witbier, Belgian Pale Ale, Saison, Biere de Garde, Belgian Specialty Ale
17. Sour Ale	Berliner Weisse, Flanders Red Ale, Flanders Brown Ale/Oud Bruin, Straight (Unblended) Lambic, Gueuze, Fruit Lambic
18. Begian Strong Ale	Belgian Blond Ale, Belgian Dubbel, Belgian Tripel, Belgian Golden Strong Ale, Belgian Dark Strong Ale
19. Strong Ale	Old Ale, English Barleywine, American Barleywine
20. Fruit Beer	Fruit Beer
21. Spice/Herb/Vegetable Beer	Spice/Herb/Vegetable Beer, Christmas/Winter Specialty Spiced
22. Smoke Flavored and Wood Aged Beer	Classic Rauchbier, Other Smoked Beer, Wood-Aged Beer
23. Specialty Beer	Specialty Beer

BJCP also lists 5 categories of Hard Ciders and Meads (an alcoholic beverage, made from fermented honey and water).

Source: Beer Judge Certification Program (BJCP) - 2008 Classic Styles Spread Sheet
1000+ beers listed by category/style

Terms:

ABV - Alcohol By Volume %
ECB - European Brewing Convention is another measure of color. ECB = 1.97 * SRM
FG - Final Gravity - Specific gravity after fermentation.
     It determines a large portion of the feel of the beer in the mouth,
     particularly whether the beer is sweet or dry.  
IBU - International bittering units
    The bittering effect is less noticeable in beers with a high quantity of malt,
    so a higher IBU is needed in heavier beers to balance the flavor.
    For example, an Imperial Stout may have an IBU of 50, but will taste less bitter
    than an English Bitter with an IBU of 30, because the latter beer uses
    much less malt than the former.
OC - Original Gravity: density of the wort before the beer has begun fermentation.
SRM - Standard Reference Method - A scale to describe how light or dark a beer is.

When using color charts BJCP says "An exact match is unlikely, so look for the closest lightness/darkness match rather than attempting to match hue."
See:
2008 BJCP SRM Beer Color Descriptors
BJCP Color Guide
Standard Reference Method at Wikipedia
chart at BrewersFriend.com
Beer Color and the Beer Color Reference Guide at BellaOnline
Beer Color: Understanding SRM, Lovibond and EBC | Home Brewing Beer Blog by BeerSmith

Links:
1000+ beers listed by category/style
Beer style: Facts, Discussion Forum, and Encyclopedia Article