Take a rhythm in 4/4 (say a standard rock snare backbeat, playing on the second and fourth note of a four note bar), layer on a cymbal pattern which repeats every three notes, then a bass drum pattern which repeats every five notes. The effect is fairly subtle because the snare keeps everything sounding like 4/4, but the feel of the rhythm is constantly shifting.

I found a nice YouTube video demonstrating this a while back, but unfortunately all I can find now is videos of polyrhythms where the loops all have the same duration but different numbers of beats per duration... which is an interesting technique in and of itself :)