Tag, you're it
I'm considering attempting to add some sort of tag functionality to the site. If you're not familiar with tags, go read up on them. The quick and dirty explanation is that tags are a way to classify and sort data. Journal entries are data. Tags would basically be quick keywords to identify the content of a particular entry. For example, this entry could be tagged with “php, upgrades, tags” just to name a few. The idea is that you could then search by any one of those tags to find related posts — say, any posts I've written about upgrading the site.
I don't think it'd be that hard to add tags to the entries themselves. The tricky part would be coming up with a search function to make use of the tags. I might give it a try sometime later this week when I get some free time and don't feel like doing anything else.