I'm a big fan of to-do lists and use a range of different apps and tools to keep my work and personal life on track. These tools can get quite complicated and I like to have a simple to-do list manager on hand as well, for all those things which are short term and which need doing but don't require serious, detailed, or complex management.
Sticky Notes HD is a good example of this kind of app. It is great for little on-screen reminders to buy milk, or a birthday card, or whatever it is you can easily pick up on your day to day travels. It is also good for making jottings that you might move on to another app later or simply use once then delete. Ideas for a project, a packing list for the summer holidays, shopping list for a children's party – those kind of things.
You can colour code notes so you can keep shopping visually different from everything to do with that party, and you can set reminders too. If you are using the Windows Phone version this app supports live tiles so you can pin notes to the start screen.
Product: Sticky Notes HD
OS: iOS, Windows Phone
Price: £0.69 iOS, free for Windows Phone