Platform: iOS, Android
If you have trouble staying on top of tasks and remembering what's on your to-do list, Evernote is the app for you. It lets you make several types of notes using text, photos and audio recordings. There are also several ways to organize your notes, and you can even use your device's GPS device to attach a location to them.
Best of all, Evernote has great multitasking capabilities. You can record notes while you're performing other tasks or using other apps on your device or phone. Once you've made a recording, you can sync them to your computer or other devices, and share files like PDFs.