There is a Secular Solstice in Berlin, Germany, but it happens in a small apartment so it has to be invitation only and is already full AFAIK.
Frankfurt, Germany might again be doing one but I do not know particulars.
Leipzig, Germany is not having one this year due to the place where the last couple of Solstices happened being currently infested with toddlers.
Berlin location has been changed, but the space is still somewhat limited (date: 15th December). Contact Anne (Lachoutte?) if you really want to attend
Frankfurt definitely has a Solstice celebration, but I don't know the details.
There's a solstice celebration happening in Cambridge (UK) on Sat Nov 15th, location is TBD due to venue difficulties
Facebook event: https://www.facebook.com/events/1955164527864109/
There will be a Solstice event in Kyiv, on December 29th - tea, cakes, and Harry Potters from different points in time comparing their notes. (Not invitation only, but better warn me if you want to come - it's at my workplace.)
Many LessWrong communities are holding Winter Solstice holiday events. What exactly that entails varies from community-to-community, but often includes:
If you're hosting such an event, this is a good post to comment on linking to whatever event-pages you have set up to collect RSVPs or tickets/donations.
It's helpful reserving a spot ASAP (as well as donating to help pay for the cost of the venue), so that the organizers can plan better. Many events have a pay-what-you-can scheme, with newcomers or people without much spare cash encouraged to donate around $15, and more well-to-do community members can help subsidize the event for others.
Events So Far
US East Coast Megameetup
December 15th – New York City is hosting their annual Solstice + Megameetup. Travelers are welcome all weekend long to stay at a large house being rented for the occasion. The ceremony itself is will be Saturday evening.
Bay Area
December 9th – The San Francisco Bay Area is holding their solstice event at a planetarium in Oakland. There should be a sufficient number of seats, but seating is finite, so please get an official ticket on Eventbrite to confirm there is still space.
Boston
December 21st – A smaller, more intimate event, Boston wins the "actually celebrating Solstice on Solstice" award.
Seattle
December 22nd – Honorable mention for "almost on actual Solstice."
I believe there are Solstices in the works in the UK and Germany but do not know many details about them. If you're running one, please comment!