It's a free e-mail sent by La Página del Idioma Español. The site was founded by Uruguayan journalist and Spanish-language expert Ricardo Soca. The e-mail presents one highly useful word a day and gives you a lot of interesting historical and etymological background on the term. It's a quick, fascinating read, and it makes us feel a bit smarter every day.
To sign up for free, please visit the Spanish-language link of La palabra del día.