Learning Python with Project Euler: Problem 1

This one is short and simple. There was really nothing to learn as far as Python goes, the constructs are similar to Ruby, though I'm sure there's a nicer way to write it. I'll also write my Ruby implementation which is a littler shorter. I'll likely try to write more efficient implementations in both languages.

The problem:
Add all the natural numbers below one thousand that are multiples of 3 or 5.

My Python implementation:

vsum, i = 0, 0
while i < 1000:
  vsum += i if i % 3 == 0 or i % 5 == 0 else 0
  i += 1
print 'sum: ' + str(vsum)

My Ruby implementation:

sum = 0
(0...1000).each { |v| sum += (v % 3 == 0 or v % 5 == 0) ? v : 0 }
puts "sum: #{sum}"

Contribution by Lov Loothra (250+ times faster than mine):

import sys
def main():
    N = 999

    #sum of all multiples of 3 < 1000
    sum3 = (N/3*(N - N%3 + 3))/2

    #sum of all multiples of 5 < 1000
    sum5 = (N/5*(N - N%5 + 5))/2

    #sum of all multiples of 3 & 5 (i.e. 15) < 1000
    sum15 = (N/15*(N - N%15 + 15))/2

    #final result
    print sum3 + sum5 - sum15