I like to collect coffee mugs from all the previous incarnations of myself (jobs, vacations). But you might have noticed that tea and coffee tend to leave not-so-pretty stains on ceramic cups. So, I wind up with a lot to clean. Luckily, it's actually fairly simply to whiten my collection, and the task doesn't require a big smelly jug of Clorox.
Just fill the tainted cup with warm water and drop in a denture-cleaning tablet like Fixodent. Once the tablet stops fizzing, it will be whitened, and the tablet will also kill away bacteria. Want your toilet bowl to sparkle too? The tablet works on porcelain toilets too; just drop it in, let it fizz, and flush! Don't have denture tablets around? You can also use white vinegar to do the trick!