import re
dom = '''<cite>domain3.com</cite>sad ja sad. asda  da.das asda. asdasdaswq.
sadas awe.q eqw .eqweqwe .qw eqwesa . <cite>www.domain3.com</cite>
<cite>qwe.domain1.com</cite> Lorem ipsum sit amet
<cite> http://qwe.rty.domain1.com</cite>
<cite>qwe.rty.domain2.com/index.html</cite>'''
out = re.findall(r'''<cite>.*?(\w+\.\w+)[\s/<>"']''',dom)
print set(out)