I am a monster fan of EverNote. It allows you to keep multiple Notebooks, and I have five that I keep, which correspond to different lengths of time, They are OneDay, OneWeek, OneMonth, OneYear and Information
OneDay is everything that I need to keep track of, and get done today. If I get a phone call or jabber, I quickly add it to the OneDay notebook. Ideally, OneDay is clean every morning. I say ideally, because I typically fall short of the goal, but that doesn't stop me from trying.
OneWeek is everything that can't be done today, but needs to be worked on when I get a chance. Stuff like say, adding some new verbiage to our support emails or doing a hallway usability study of the new data app that we're going to roll out.
OneMonth are obviously longer term projects that I really like to do, but don't think I'll get the chance to any time soon. These tend to be the "Google" type projects that I'll work on for a little bit on a Friday.
OneYear are typically massive structural changes to the organization, or the technical architecture that I'd like to make, but need more planning then I have time for now, especially since they aren't priorities. These include projects like "Switching messaging middleware from ActiveMQ to RTI" or "Build automated stock trading service". Sometimes on the train I'll do some research pertaining to these and I'll jot down what I've found in the OneYear notebook.
Information just stores server IPs, local restaurants, websites I should check out, or in general its like the "junk drawer" of my thoughts.
EverNote syncs all your notes centrally, so the data is seamless between your office, home and mobile phone(Windows Mobile or the iPhone). Best of all, its free.
It can also store voice and video, but I don't make use of that, so I can't speak to its ease of use.