My currrent title is "Test Engineer, EE" but I have worked in many a startup/skunkworks where my ME, ChemE, and CogPsych, etc., backgrounds were valuable (and sometimes also in big companies when out-of-usual problems occur). Because of this I am very interested in resources that I can use to refresh a rusty memory, especially if they're compact.
For M.E., I'm partial to the books from Stock Drive Products. Their explanation of the properties and purpose of the involute gear tooth is excellent and entertaining (in a pure-geek [Gieck?] way)!
A good wide-applicability resource is "Engineering Formulas" By Gieck. The left-pages are blank, amenable for suppplementation and notes (in my older edition, I have added lots of Boolean formulae and Laplace/Fourier/Z stuff, and some tables of integrals).
Why isn't it "Handbook of Machinery" or "Machinery Handbook"? I'm a through-and-through EE, but the name "Machinery's Handbook" has set my teeth on edge since the first time I saw one. Throughout my career, except for a few-year stint at a wirebonder manufacturer where I was one of a handful of EE's, if something's moving, it's a bad thing!
Machinery's Handbook also tells the story of American industrialization as revisions occur on a four-year cycle. A thorough history is available at http://new.industrialpress.com/resources/history.
In keeping with developments in mobile technology, Machinery's Handbook and pretty much the entire library of new titles from Industrial Press are being formatted for smaller portable screens. Senior Editor Chris McCauley said "we are simultaneously developing digital technology for popular presentation formats (Epub, mobi and PDF) and portable devices running iOS, Android and Windows. Given our celebrated print presentations for complex engineering math and detailed charts, tables, illustrations and spread-sheets, building durable digital versions is a giant challenge."
My favorite handbook is Reference Data for Radio Engineers, 4th edition, also known as the ITT handbook. It was published in 1956. I got my copy as a technician in the mid 60s, and I still use it. It's eminently practical, and is one of the basic volumes of my engineering library. Even as a retired engineer I find it useful.
Although 'only' an electrical engineer, I have a Machinery Handbook which I still use every now and then. My copy dates from mid-1950's and it was given to me by my uncle (who was a machinist of some considerable skill) in the late 1960's. I have used it quite a bit over the years - calculating strengths of beams, torsion, screw and tap sizes, etc - mostly related to hobby activities (i.e. push rods for model airplanes, drilling and taping metal and wood, deflections for antenna supports, etc). And even, back in the day, looking up cosine, sines, logs, etc.
There was also the books from Chemical Rubber Company (CRC) which had tons and tons of trig tables. And, of course, for us electrical types, ITT's 'Reference Data for Radio Engineers'. Even though I am retired (and thereby ancient indeed) my copy is right over my shoulder here in the computer room.