Here is another possibility: Agapanthus
Here is a link to the Google image search for it...
http://images.google.ca/images?hl=en...&sa=N& tab=wi

If the link doesn't work just go to Google, click images and type in agapanthus

It is a common garden plant around these parts, (Victoria, BC, Canada) and is somewhat weedy, thriving on neglect. Thankfully it is easy to rid of, just dig up the rhizomes - it is a perennial though so check again next year to see that you got it all. If its been around for a years you can expect to see big clumps up to ten feet across so it may take a bit of digging.