I attended a briefing last week in which I learned that the Human Genome Project was made possible by a $3.8 billion dollar grant awarded over 13 years by the DOE/NIH. Since its completion in 2003, the world has seen roughly $796 billion in economic activity driven either directly or indirectly by the HGP, much of which has been in America. In 2010 alone, HGP-related economic activity generated roughly $67 billion, and supported 310,000 jobs. (http://www.battelle.org/spotlight/5-11-11_genome.aspx) It has created or bolstered entire industries, ranging from personal genetics testing, paternity tests, forensics, biofuels, healthcare, agriculture, and many more.
Oh, and we've sequenced the human genome, which is quite a leap forward for humanity.
In terms of bang for your buck, I don't see a better form of federal spending.