Android/iOS/Windows Phone/Blackberry: I'm pretty generous when it comes to my friends -- I loan music, video games, you name it. But sometimes that means I forget to get said item back when I want it or forget that item is mine when I go visit. You Borrowed It is an app that can keep track of it all.
Add an item to the list, along with who borrowed it (you can choose from your contacts), when they borrowed it, when you'd like it back, and even attach a photo if you want. The app will even add a reminder to your calendar when the borrowed item is due back so you don't forget. Normally, that would be enough to make an app like this useful, but when the due date is up, You Borrowed It will offer to ping your friend (via email, text, Twitter or Facebook) about the item. You can customise the note so it doesn't come off like you want your stuff back or you'll break their thumbs.
Strictly, there's nothing You Borrowed It does that a simple checklist or calendar reminder won't do on its own, but it's nice to have an app that combines the reminder, the list of borrowed items, photos of their original condition, and names and dates all in one place. If you're interested, you can grab the app for a buck at your respective app store link below.