I learned hiragana and katakana by drilling RealKana [0], together with the Flash-based Drag-n-Drops [1] back when Flash was still a thing. It looks like the original author of [1] has non-Flash versions now [2].
RealKana is great for drilling recognition (kana -> pronunciation), and I learned the individual kana by loading one column at a time (e.g. ka/ki/ku/ke/ko). Drag-n-Drop is good for speed-testing recognition, but also for recall (pronunciation -> kana), since it's invertible: you can either choose a pronunciation and go find its kana, or choose a kana and find which pronunciation it goes to.
I'm not sure you can really "learn" these characters without drilling like this -- the symbols are arbitrary, so you have to memorize the association between glyph and reading by brute force.
[1] https://www.csus.edu/indiv/s/sheaa/projects/genki/hira_main....
> Hiragana being far more useful to know starting out, if you had to pick one.
Before visiting Japan, I learned to read in both Hiragana and Katakana, but I didn't really know more than a dozen or so words in Japanese. While visiting Japan, I found Katakana to be a lot more useful, because it's commonly used and often is just English words converted to Japanese letters. I think all my Hiragana reading abilities were completely useless as I couldn't tell what I was reading.
Why is this trending on HN? It's one of a thousand resources on Japanese, and a poorly built and incomplete one at that. Is this blogspam?