Even though the shops are trying hard to turn this into a day off so that you can go spend money, the intention of having this day is to contemplate the progress of Civil Rights in this society.
If you aren't planning on doing a Habitat for Humanity project or feeding the homeless, at least you can have access to the speeches of Martin Luther King.
I was a wee brat when the Civil Rights Struggle was happening, and at that age, you're more interested in cartoons. In a way, it meant that I would have a better appreciation for the speeches as I'd visit them as an adult.
This particular video is his last speech, and is probably one of the better ones to present here since it is of only 3 1/2 minutes. If you want to pursue, this one video has a lot of good links on it. If not, well at least I have presented it here.
As I'm writing this, I'm listening to the entire I Have A Dream speech in background. The man was an amazing orator and well worth a listen if you have the time.