Gosh, I’m no tax expert so I defer to what the IRS says on this subject. See the discussion on Tuition and Fees Deduction at irs.gov for the latest and greatest information on that subject. Also, you can deduct educational expenses paid for using interest income from US Savings Bonds (but that doesn’t do people much good unless they already hold some since most such bonds come with 5 year or greater maturities).
According to my tax accountant, Rita Brantner, if you’re self-employed you can write off classes and cert expenses as long as they’re related to your job activities under the heading of “professional development.” But alas, this benefit does not convey to salaried employees who work for somebody else.
That’s about it, here in the US, as far as I can tell (and my tax accountant confirms my conclusions).