Trello is a great tool for this. There are plenty of similar tools as well, including open source alternatives. Your separate open file for mental stack dumping

Trello is a great tool for this. There are plenty of similar tools as well, including open source alternatives. Your separate open file for mental stack dumping is a great option as well, and something I often use. My favorite, though, is a stack of black index cards on my desk. I like the immediacy, the ease of sorting, and the ability to quickly spread things out or stack them up. Best of all, there's satisfaction in tearing up that card and throwing it away when done. I use Trello quite a bit, but nothing beats the index cards for me. It's something I use both at work and at home.