I have a neighbor who by building a pool has diverted the flow of water which could end up flooding my family room. What can I do?

Get the building inspector out there, quick !!  Take photographs and/or video of what happens on a rainy day and ask the building inspector to issue a violation notice.  It could be a matter of regrading the property or re-directing the flow of down spouts or other drainage issues, but if the water is now flowing on to your property because of the pool, you have to get the town involved.