Not that I ever need such things, but if I did, I'd probably stick to some online services, which are probably many. The big companies offer such services (Microsoft, Google, ...) but there may be smaller ones too that could fit your needs. The problem with locally installed software for that purpose is simply that it doesn't walk along with you; if you need to store such information into some other place than paper and/or need to synchronize it, it probably means you move around, and that means you should be able to access the data where ever you are. There is no device/software that does this; even cellphones that today contain calendar etc. aren't with you all the time (not in my case, anyway). Therefore the natural solution is that it's a service that you can access with a multitude of devices, depending on what you have available.
If I needed the things for work, I'd probably ask my employer to handle it for me, pay if needed---to ease out working. In private life it's just a pain to sync ten different devices every now and then just to feel that everything's with you..
To give an example that I've actually tried out, Google's calendar seemed nice. I think they have a commercial version of it available too, but can't say what the differences are. The cost-free version impressed me some time ago, and I guess it has just evolved since then.
What organiser/PIM do you use?
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