There are several web applications that allow you to create timelines online.  I’ve listed several on my Examples of Student Work page under Student Timelines.

I see few advantages over making these online as opposed to having students use color pencils and paper, and then tacking them on the classroom walls.  However, in addition to being just a change of pace, the fact you can import images from around the Web in at least some of these applications does make it somewhat appealing.

I’m particularly impressed with XTimeline.