My brain holds a lot of my lists.
At work, I know what needs to be done... and use my email/calendar for reminders for follow ups and stuff. So, when my boss becomes a nosy nelly... I leave a post it on my desk of what my next few tasks will be. Then she doesn't bother me as much. Otherwise, she will come to tell me what I know I have to do already. (DUH!... it's my job!)
At home... my brain, and occasionally, pen and paper. Never usually electronic.
Scrapping/CT/Admin Stuff... A "note" on my desktop with Designer Req's listing what is still needed to do, and my tutorial list. I erase items are they are completed. I use my email to keep my credits for each month. LOL... I have no idea how that started, but I have all the layouts I've made for each month, and what products listed as draft form in my email from the last 3 years, i think. For challenges that I'd like to complete, thumbnail/link on my desktop, and then those get trashed as I finish them.
Digital Albums that I work on for printing... I use color codes so I can see what months are needed more pages... so I have some representation for each month in a yearly album. Though... Summer months, warm weather has way more pages.
I'm weirdly organized. But... it works for me.