I have written many posts about the mighty Oxford English Dictionary, and this one described a way of getting access to the online version for nothing.
There is another way: simply sign up to the OED Word of the Day and you will be emailed daily with a link to the dictionary's entry for a word or phrase which, for one reason or another, is considered interesting. A recent example is Ps and Qs; the etymology of this is uncertain, and the OED lists seven possibles, likely or unlikely.
But does this mean, I hear you cry, that they will email you the entries for every one of the OED's 600,000 words and 3 million quotations? Well, yes, they will, but it will take them over 750 years, even if there are no new entries (the last quarterly update noted that 1,200 new words and meanings had been added).