Python 3, 22 (Possibly not allowed)

If the challenge is "to create a python script which prints the even numbers from 0 to 100" and not "to create a python script which prints the even numbers from 0 to 100, newline separated", then the shortest solution is:

print(*range(0,101,2))

Remember, it's very important in code golf not to put any limitations on yourself you don't have to - do what the problem asks, and no more.

Python2 26

i=0;exec"print i;i+=2;"*51

independent discovery of @bitpwner's solution

Python 2 - 26

i=0;exec"print i;i+=2;"*51

Based on the tip on exec with string multiplication found at Tips for golfing in Python.

Python 2 - 12 characters

print 8**999

The decimal representation of all even numbers from 0 to 100 can be found in the output:

153778990270139647116444851659594064330089236967104214470764753645007350076834118596920008479824182447803706156756475613564110522612279602948135310258168541404369918794480627176627915013920083365328091029969610052054309789461709376676636344651086297099162082351332867728061686056465813162964114500668343488577962834185114919242101638217077550294093097112980059735456387540301162747936045475366317560310988720435512281742591085641505551107966844283901574058972330493685836063965131445246304097593431852972101058022587137885482726523043570690342524474585327775688980689010069001288756281975198668705741000141718184277589376710426738442847382969979234512669279398030637083755270090078676447687796406001053805898105262326290072552249025832780916090265261064205460488458795026145331708830141367124625271312584437671840499845750728447412590406684361326531266896486146862384988911439049971734022314877278748672

As a bonus, so can the odd numbers.

Python 2, 26 (possibly not allowed)

i=102
while i:i-=2;print i

It wasn’t strictly specified, in which order the numbers were to be printed.

Python 2 in *NIX, 24

os.system('seq 0 2 100')

If you need to add

import os

Then the total is 33 characters.

Python 2, 28

for i in range(51):print 2*i

Python 2 - 20 (Possibly not allowed)

This is python 2 specific and probably cheating since it prints the list, but since all numbers end up on the screen:

print range(0,101,2)

Python 2 - 24

0;exec"_+=2;print _;"*50

(based on bitpwner and Sparr solution)

In the shell, "_" contains the value of the previously evaluated expression

Python 3, 29

*a,=map(print,range(0,101,2))

If you're in Python 2 and happen to have already imported the print function, you don't have to make the iterator object into a list and it becomes 25 characters:

map(print,range(0,101,2))

I don't know that that's entirely fair though.

Here's another fun idea that works in python 2 or 3. It's a tad longer.

def p(i):
    if i+2:p(i-2);print i
p(100)

Python List Comprehension - 39

This uses a list comprehension, one trick to make it shorter is to multiply the index by 2 rather than going from 0 to 100 and a trailing if x % 2 check for even.

print'\n'.join(`2*x`for x in range(51))

Using a map and @isaacg's suggestion it ends up being the same 39 characters:

print'\n'.join(map(str,range(0,101,2)))

Edit: After separating values by newline it is by far not the shortest.

Python 2 - 20 (questionable)

If isaacg's space-separated solution is OK, then presumably the normal list formatting is as well:

print range(0,101,2)

For further rule-twisting, apply SirBraneDamuj's suggestion from the comments:

print range(101)

and you are at 16. So what if there's some extra garbage separating them?