yLend is a small and easy-to-use application that will keep track of all your loaned items.
You can add a loan in seconds: enter name, item and date and the loan is permanently recorded. When the item comes back, delete the entry!
In the interest of harmony with family and neighbours, I suggest you enter any loans AFTER they've borrowed your stuff and departed. Writing down dates and serial numbers in front of them isn't all that polite.
On the other hand, if you're lending to a hoarder who never returns anything, feel free to make them wait while you enter the details into your computer right in front of them.
yLend is deliberately kept simple, because otherwise you wouldn't bother to add records.