Of Tagging and Journals

A lot of writers keep diaries.  And even if they don't keep personal diaries (you never quite know who's been reading something they most definitely should not have been), they almost always have some form of writers journal. 

For about a year now, I've been on a personal mission to find a piece of software -- or anything electronic in any size, shape or form that will better enable me to keep my writers journals.  The only two conditions are that it has to be simple (in approach and visually), and that it must not keep things in a proprietary format.  I've stumbled across some useful stuff that qualifies for the first condition, but they all fall over on the second.  Which is too bad, because it means I still won't make the transition from my A5 sized spiral notepads to something a little more tree-friendly. 

As it happens, I do keep a diary too.  But that one is on the computer and has recently been amalgamated from several discretely themed ones.   But that gets kinda confusing too.  And my tech minded brain started to think of input fields and databases and all sorts until...... stop!  I had the answer: tagging. 

Yep, wonderful tagging.  In my simple text editor I add my diary entries in reverse chronological order, and tag particular paragraphs with [tig] brackets, rather like Vox posts ;)  So instead of [this is good] I'll put in something like [dreams], [characters] and that sorta thing.  Searching and identifying paragraph content suddenly became a whole lot easier.

But surely there must be a better (although I defy you to find a simpler) way to markup content?  Do you keep a diary or journal, and how do you go about organising the mass of content?