As I've gotten older and perhaps more sentimental--or perhaps less capitalistic (despite having loads of stuff...)--I've found myself increasingly inclined to mark it somehow. At the moment, my only particular habit is straight out of TIGANA: I light a candle on the Ember Days to, er, defy the gods. Because that makes sense. :)
(I just said so to Guy Gavriel Kay on Twitter. He says he'll now feel responsible if there are any lightning strikes in my neighborhood. *laughs*)
Anyway, though I rather love the idea of staying up all night to guide the sun back home, bahahaha no. Similarly with a candle in the window for the same purposes, but the paranoid in me isn't comfortable with leaving it burning with nobody to keep an eye on it.
I've left it a little late for this year, but I'd like to develop some kind of family ritual of a meal and...gifts that are not so much for ourselves as things to make the world a little better place. Donations to Heifer International, or support for something like the Dublin Urban Rooftop Farm initiative, which just successfully funded. Go out that day to buy gifts for local childrens' charities. Things like that.
I'd also like to make the meal something...not run of the mill. Someone on Twitter does era-determined themes (this year she's doing an Elizabethan feast!), and I think something like that, or something with an international focus on foods, would be really wonderful.
Anyway, so do you have solstice traditions? What kinds?