As compiled by Science News:
https://www.sciencenews.org/article/top-stories-2015-pluto-gene-editing-new-hominid-and-more [sciencenews.org]
javascript required for the domain sciencenews.org.
One story I missed was, ranked at 24, an algorithm to test equivalence of two graphs - a well known problem for which no known manageable solution had existed.