RvTk (Reviewing The Kanji, and sometimes Koohii) is an invaluable website where students can share their Kanji stories and mnemonics. Perfect for the lazy and less imaginative, as I am. But once you finish RTK1, you might be tempted to switch to a more comprehensive SRS tool, like Anki. Among others, it provides online and offline reviewing, mobile apps for reviewing on the road, and many options to fine tune the SRS.