Usually I use Google calendar for my schedule check. I like its user interface and usage very much. I think that is the best free scheduler ever. And it is able to be use anywhere via browser over Internet connection.
Now I install eGroupWare on my office internal. It is actually usefull for group scheduling, maybe it become a must-use tool for us. It is a great software I think.
However those usefullness is becoming a trouble. The two scheduler can not synchronize each other or import activity data automaticary.