Once you've digested that you probably want to try practicing the first two units in our rhythm anthology.
Apps and Programs
In general it seems that apps designed for rhythmic practice are a little more difficult to design than the note-reading quizzers we've already seen. These are all a little crude and weird but they may be worth trying.
PC / Mac
Robert Whelan has a rhythm driller at emusictheory.com. As always this will work with any java-enabled browser.
iPhone / iPad
Rhythm Sight Reading Trainer ($3) is the best thing I've found. The interface takes a few minutes to get used to, though.