These probably aren't the best ones out there, just what came to mind easily:
For people who take a few different medications, those weekly pill box things - it takes less attention to do it all at once when non-groggy.
Keeping one's workspace clean and organized might be an example; a lot of people say they can pay attention more easily when things are clean.
Keep bicycle tires well pumped - makes you go a lot faster. (Also, having the correct kind of tires. Mountain bike tires are slow on pavement.)
Set up the computer/browser to automatically open the tabs/programs you use the most. (I know some people who do this on their work computers.)
"no 'poo" hair washing makes hair less oily so you need to wash it less often. Also cheaper. (baking soda + vinegar is the usual method.)
buying two weeks' worth of groceries at once so you don't have to shop as often
Dvorac and other alternative keyboard layouts
email inbox automation things (I've not used any, but people seem to like them)
— Wikipedia
This thread is for posting any promising or interesting ideas for lifehacks you've come up with or heard of. If you've implemented your idea, please share the results. You are also encouraged to post lifehack ideas you've tried out that have not been successful, and why you think they weren't. If you can, please give credit for ideas that you got from other people.
To any future posters of Lifehack Ideas threads, please remember to add the "lifehacks_thread" tag.