stands for Youth Leadership Foundation (various locations)
YLF stands for Yttrium Lithium Fluoride
YLF stands for Your Loving Father
YLF stands for Yahoo Lending Facility (satire)
YLF stands for Russian Young Leadership Fellows for Public Service Program (aka Russian-US Young Leadership Fellows for Public Service; International Research & Exchanges Board; Washington, DC)
YLF stands for Youth Life Foundation (Washington, DC)