In Claris Organiser for Mac, and now in Palm 
Desktop but ONLY for the Mac, not the 
windows version, you can attach entries to 
each other.  For instance, if you have a an 
appointment, that can be attached to the 
contact with whom you have it, and when you 
do a note of the meeting or phone call (you are 
going to do a notes feature pretty soon I 
guess.?) you can link that to the contact as 
well.  The result, its easy to find anything from 
anything - you have a contact, go to all your 
notes of meetings with him, you have one of 
the meetings, go to all the details of 
everything.  And these can easily turn into 
project type stuff - because you can link 
multiple contacts, notes about all kinds of 
things.  Much more flexible than categories.  
You can also paste in correspondence if the 
notes function is big enough.