Ask HN: Keeping a research/work log

I see a lot of discussion about to-do lists, but less about keeping a record of your work.

Sometimes at the end of the day I will sit and write up a few short paragraphs summarising what I've done and what I've learned. - technical notes and general thoughts about my work and study. I want to start doing this more frequently, but I want a nice searchable format rather than scattered text files. I already carry around a small notepad to scribble down thoughts and work through problems on paper.

What methods do you use? My current best idea is to keep this all on a local installation of Wordpress.