The following have had a significant influences in my life. Many, but not all, are recent discoveries.
General Semantics is "a popular, practical discipline that applies modern scientific thinking toward the solution of personal and professional problems." It was developed by Alfred Korzybski in the early 1900's as a positive theory of sanity — a methodology for acting sanely. Korzybski's most famous phrase is probably "the map is not the territory".
Getting Things Done (GTD)
Getting Things Done is David Allen's methodology for workflow. One of Allen's insights is that getting tasks, ideas, etc. out of one's head into a trusted system allows one to think more clearly with less distractions.
You Need A Budget
You Need A Budget is a software application which implements a virtual envelope system. This has helped me plan, manage and track my spending and has given me greater financial clarity.
The Paleo, Primal and Bulletproof Diets
The Paleo Diet is based on the thinking that anatomically modern humans spent most of their time as hunter-gatherers, and therefore we are adapted to the diet that hunter-gatherers eat. Robb Wolf presents this argument in The Paleo Solution: The Original Human Diet.
Mark Sisson's Primal Blueprint is similar to the Paleo Diet, but makes adjustments for the modern world we live in. He discusses gene expression — how our genes respond to our environment (including what we eat), with positive or negative results.
Dave Asprey's Bulletproof Diet is similar to the Paleo and Primal diets. Asprey developed this diet through research and bio-hacking, however, rather than through analysis of what paleolithic humans did and did not eat.