Paprika. I haven't been paid or sponsored in any way to write this but is one of the most fabulous apps.
As you may know, I am an avid menu planner. We have more variety and less waste by planning for the week. Up until this year I used a diary to note down our dishes and write the shopping list. Now all I need is the phone and/or the iPad. I can either read through my magazines and add in a note manually which page to go to, or search for recipes an build my virtual recipe collection from many websites where you can save straight into the app with one touch of a button. Ultimate convenience - with the menu designing, not with the food itself!