If you want to be able to figure them out without using one of those calculator things heres what you do
The colours correspond to numbers
Black: 0
Brown: 1
Red: 2
Orange: 3
Yellow: 4
Green: 5
Blue: 6
Purple: 7
Grey: 8
White: 9

Now the way to read them
The first colour represesnts our first number, second represents the second number, the third represents the number of 0's after the second number. The last band represents the deviation between rated and actual:

Gold: +/- 5%
Silver: +/- 10%
None: +/- 20%

Also Here's a handy resistor calculator if you're feeling lazy: http://www.dannyg.com/examples/res2/resistor.htm


Edit: you do know you can sticky threads, right? -250