Trefoil Knot with Traveling Bead
 
Maple 8 code:
 
with(plots): with(plottools):
P:=tubeplot([(2+cos(1.5*t))*cos(t),
   (2+cos(1.5*t))*sin(t),sin(1.5*t)], 
   t=0..4*Pi, radius=0.4, shading=XY):
pic:=n->sphere
   ([(2+cos(1.5*n*Pi/6))*cos(n*Pi/6), 
   (2+cos(1.5*n*Pi/6))*sin(n*Pi/6),
   sin(1.5*n*Pi/6)],0.6,color=red):
Q:=display(seq(pic(s),s=0..23),insequence=true,
   scaling=constrained):
display({P,Q});
 
Comments: 
  1. The bead shape could also be any of the polyhedra types supported by Maple.
  2. An animation editor was used to slow down the display time of each frame.