I used Knuckles in China Land to learn hiragana and katakana years ago. Looks like the site went down ages ago, but the archive seems to have the original download file.

Nowadays, you should probably check out Memrise for learning vocabulary/alphabet. Since I already know the hiragana and katakana alphabets, I'm using the Genki 1 course to bolster my vocab. But they have others for learning the hiragana and katakana alphabets. What's nice about Memrise is that they have a mobile app that you can take with you. It's meant to be used for about 5 minutes per day, just as a quick refresher thing.