Check out Mind Performance Hacks, a brand-new title from O'Reilly. Ron Hale-Evans, game designer and founder of the Mentat Wiki, picks up where the more theoretical Mind Hacks left off, and provides a toolkit for improving cognitive function.
Ron offers 75 memory tricks, mental math shortcuts, aids to creativity and clarity, and tips for improving mental fitness, drawing on cognitive theory and grounded in practical application. I found hack #18, "Pre-delete cruft," immediately applicable ("When you initiate an activity, determine a kill date for it at the same time." I love the idea of mercilessly purging timestamped folders without having to look or think about the contents again.) Also highly useful are the survey of different memorization systems from Lewis Carroll to Frank Gilbreth, and the decision-making hacks that employ Likerts, Gott's Principle, and iterated Prisoner's Dilemmas.
And hey, any book draws on Greg Egan's idea of the exoself and uses research to say I should play more video games to decrease the time it takes to task-switch is okay by me.
Full disclosure: I've known Ron for a long time -- ran into him in a chat on Bitnet, which tells you *how* long. But hadn't talked to him in years, and this book was a delightful re-acquaintance.