In Dropbox, I keep an annual logbook file for both work and home, just a text file (well, rtf). As I do things that I want to remember I did, I write a note, paste a command line or link, etc, under a line with the date on which I did/wrote/pasted. Over time I've built up a record of my activities, and a handy notebook for remembering how to do complicated things I seldom do. It also makes it easy to write up status reports when those are necessary.