The SRS page of the wiki has lots of links to useful things. The Supermemo pages especially have good advice on formulating knowledge as cards.

A few years ago I tried learning Esperanto via SRS, and it seemed to work well, but I stopped reviewing the cards because I realized that it was basically a waste of time - it was less entertaining than other sources of entertainment (especially once you've learnt all the cards and only have reviews left to do), and useless relative to other types of work I could do. I also tried Lojban but gave up for the same reason. Of course, your mileage/situation may differ.