Anki cards are quite easy to make yourself - just click add cards, then type in the question/prompt and answer (Anki will fill in the kana). For RTK kanji, I find it much easier to use this site, as Mighty_Matt says. If you're looking for non-RTK decks though, there are probably some available - Anki can import from some other flashcard programs (at least Mnemosyne that I know of), so decks made for other programs may work as well. I haven't used any premade decks myself, but I imagine that you could find them for common vocabulary lists, like those for the JLPT tests.
Edited: 2007-07-16, 6:11 pm