While taking a look to Eric Rechlin's hpcalc.org site, I have learned that there is a Valentin Albillo's articles and documents site within too.
Valentin Albillo was one of the original HP calculator users in Spain - together with Fernando del Rey. He wrote a lot of articles and quizzes on all kind of HP Calculators - from the early ones to the HP71. He even collaborated to write Spanish-speaking HP application books (for example, for the HP34c calculator.
If you are interested in something more than the hardware, you're doing yourself a disservice if you don't add Valntin Albillo's site to your favourites!
Some personal highlights:
But there are literally hundreds of them!