For starters, you can find kanji by their english meaning, or type the kanji character you want to learn more about. You can also try searching the kanji with certain number of strokes. Alternatively you can search using two or more combination of search terms to find kanji that is in common with the search filter.
Rikai is an unofficial web-application for KanjiAlive using KanjiAlive's public API that has 1235 kanji currently available. All the data that are available in Rikai is from the KanjiAlive API. You can find more information about KanjiAlive API and the web application by clicking here and here respectively. Rikai web application is solely for learning purposes only.