I have a day planner type form that I use as my lesson plans, adjust for what we actually do finish, then save and print at the end of each week. I label it (e.g. week 27 log), then the next week I write over the old dates and day numbers, then save it as the new week's log (it becomes week 28). The printed copy goes straight into my portfolio binder, I email a copy to myself to store online, and I keep a folder on my PC desktop with all of the current school year's plans/logs. I keep most of my book list for recurring textbooks on the bottom of that page so that the top gets filled in with abbreviations that I just cut and paste. It takes me about 5 minutes at the start of the week to set up the new page, but that is rolled into my lesson planning time. It takes another 5 minutes at the end of the week to proofread and print.
SAMPLE LOG.doc