I recommend using a planner and making yourself stick to it. I myself use FranklinCovey paper planner products, and I recommend them highly, but if you must go digital I recommend a Palm OS-based PDA. I've used a Palm and several other PDAs, and eventually I discovered the paper planner worked best for me. Of course, YMMV.
In my experience, the key ingredient in making your planner system successful is taking the time to learn all its quirks, read the instructions, and give yourself time to work it into your routine.
If you have a FranklinCovey store in your area, I recommend you go talk to them. If not, you can learn a lot from their website. If you get a Franklin system, be sure to read the Quick Start Guide you get packed in with your pages and read the Planner Guide Pages. The way they have it set up gives you a lot of tools for not only tracking daily tasks, but tracking where you are in the larger roles and goals of your life.
I find my day goes so much more smoothly (and I'm a lot more calm and focused) if I spend the first few minutes at work with my planner.
No matter what you do, dedicate yourself to it for at least 30 days and see if and how it's helped you. The positive benefits don't always occur overnight but it's worth the effort.
Good luck,
-lost