Not really homemade, but you can buy whitening pens that you just brush on your teeth. I used one twice a day for three days and my mum asked if I'd had my teeth bleached. Really good for tea/coffee stains.
Sorry. Only just seen reply. You can get them from amazon/ chemists for about £9.99. You literally just brush it on the teeth that you can see. They last for ages. So easy to use. I'll attempt to do link, but am on my phone, so not sure if it'll work!