While it may not work miraculously overnight, bruises do heal a lot (for me, usually twice as fast) when you dab a cotton ball with vinegar on your bruise and do this every night until it heals.
Yes, I know it reeks. But seriously, soak the cotton ball, tissue, whatever, with a little bit of white vinegar.
Apply soaked, stinky goodness to bruise and either let it sit or dab it, as long as the bruise ends up good and soaked.
Repeat this every night until the bruise goes away.
This works great on little bruises that you want to go away faster (yes, hickeys are technically bruises and yes, this works VERY well on them) but it is less successful on larger bruises and I wouldn't recommend it for black eyes (stingy!!)