Hi! Thanks to everybody for your responses. Actually, the example provided by vwphilips is pretty similar to what I need, but it is a bit too basic.
You can find one of the examples I talked about in my first post following this link: http://taitems.github.com/jQuery.Gantt/
. This chart suites my needs except the (essencial) fact that hours and minutes are not correctly represented. Unfortunately, I have not enough time to modify the source code to suite my needs.