After evaluating tools and stuff, finally settled with Dropbox synced plain markdown files. I have a generic file per week (making one per day was too much hassle), also separate files for specific projects.
I also recommend G.M.Weinberg's the Fieldstone Method on Writing.
On reading the title, I thought “oh jolly good this will be a solid discussion of log structured filesystems, RDBMS transaction streaming, and double entry book-keeping etc” so I am twice nonplussed.