There is a search field at top right of iCal - of course it's pretty basic and will apply across all calendars. if you want something more configurable you could have a look at MacJournal:
I've not tried this but it looks interesting.
Roger, thanks for the info. I've downloaded the trial version of macjournal, but initial impression is it is more than I need or want to pay for. However, using your other idea, I've created a calendar called journal and make annotations as needed and find if I title them right, the search function is fairly effective, though as you say, it gives infor across all calendars. Thanks again