gistfile1.py

import urlparse
import collections

urls = (l.strip() for l in open('urls.txt') if len(l.strip()))
data = collections.defaultdict(set)

for url in urls:
	domain = urlparse.urlparse(url).netloc
	data[domain].add(url)

while True:
	current_list = [data[k].pop() for k in data.keys() if len(data[k])]	
	if not len(current_list):
		break
	print current_list