Practicing dana can be a great way to brighten up a gloomy mind, and there are always opportunities for dana near at hand. You could do something as simple as taking a crust of bread outside to feed the birds.
"I tell you, Vaccha, even if a person throws the rinsings of a bowl or a cup into a village pool or pond, thinking, 'May whatever animals live here feed on this,' that would be a source of merit, to say nothing of what is given to human beings. "
Here an excerpt from Thanissaro Bikkhu's lovely essay on the role of dana as a foundation for the path:
http://www.accesstoinsight.org/lib/auth ... generosity
Over in Thailand, children's first exposure to Buddhism, after they've learned the gesture of respect, is in giving. You see parents taking their children by the hand as a monk comes past on his alms round, lifting them up, and helping them put a spoonful of rice into the monk's bowl. Over time, as the children start doing it themselves, the process becomes less and less mechanical, and after a while they begin to take pleasure in giving.
At first this pleasure may seem counterintuitive. The idea that you gain happiness by giving things away doesn't come automatically to a young child's mind. But with practice you find that it's true. After all, when you give, you put yourself in a position of wealth. The gift is proof that you have more than enough. At the same time it gives you a sense of your worth as a person. You're able to help other people. The act of giving also creates a sense of spaciousness in the mind, because the world we live in is created by our actions, and the act of giving creates a spacious world: a world where generosity is an operating principle, a world where people have more than enough, enough to share. And it creates a good feeling in the mind.