The most simple thing might be a belt or a pouch of some sort. Do you have a dog... perhaps try making a collar. Another idea if you live somewhere that gets cold maybe you can try making a pair of mits.
What you need to do is learn about hand sewing leather. Read the section on sewing leather here as there are some good tutorials floating around. Also do a google search for hand sewing leather for even more.
You can make a lot of things with a knife, some thread and 2 needles.
Like Dwight said, if you have a leather store close by then you should visit them.
have fun...