I generally use Microsoft Office as i know that the formats will work on both a PC and the Mac i use. Excel is a great program and there is sooo much you can do with it, especially when you have to deal with anything with a budget, but even for simpler tasks like attendance sheets and run sheets.
Word is great if u want to take your excel sheet and give it a nicer heading, graphics or have other typing to do. I type up my performance and rehearsal reports on Word.
iCal, Outlook's Calendar, and some online ones are all really good calendar tools (iCal by far the best in my mind) for anything having to do with scheduling. Make good use of the color coding and "Type" fields.
There is a program made for the mac called FinalDraft which is specifically made to format scripts and screenplays, though i havent used it yet, and have done a lot of script formatting in Word, i have heard some good reports for this program as well.
Good Luck!