Hello, everyone! Nina, Kyiv EA group organizer here.
Thank you so much for raising this issue and thank you for your concern!
About Ukrainian charities:
Assessment of the effectiveness of local charities in Ukraine was on our priority list, but… you know, all this happened. So we don’t know how effective the charities in Ukraine are. (UPD: EA Poland and some other EA communities are working on roughly estimating charities helping Ukraine, there is also a list of recommended charities. Also you can submit an organization in this form.) I know that Open Cages Ukraine are grounding their actions on EA principles, but that's all we know for now. (As dpiepgrass has pointed out in the comments, they are working on reducing animal suffering.)(If you happen to know about other EA charities in Ukraine, please tell!)
So, the official bank accounts (here to support the military and here to support the medics) for supporting Ukraine that three days ago started our government are probably the best we have right now. Also, there are a lot of local charities that provide medical help, help for the children affected by the war, help refugees and so on (sending the links here, here and here). Also some countries started gathering help for Ukrainians, maybe you can find some local facilities involved in it in your country.
Russian media controlled by the government
Many people in Russia don't know what is really going on because of the misinformation about the invasion. For example, they say that no one is firing at Ukrainian civilian facilities, only at military facilities.
There already are some organizations that debunk fake information: stopfake.org, informnapalm.org, (and there are great links in other answers to this post). Also I think it is really important to support people in Russia who are right now protesting against the war, their human rights activists, their independent media and politicians from opposition.
Two days ago I thought that international political support is crucial. General considerations were: demands to close Ukrainian sky (I'm really really not at all sure that this is a good idea anymore), to impose sanctions especially against the politicians in Russia who are supporting the war.
The situation is rapidly changing, political support is impressive right now, but it's hard to tell if it’s enough to stop the invasion. But if your government isn’t taking as much action as you think it probably should, I think it still might be an area you can influence a lot.
I’m also really really really looking for people from longtermist orgs, especially people who specialize in great power conflicts - some of our community members are in Ukraine right now, and it would be great to know about some longtermist considerations to guide our actions!
UPD: added some other links with other ways to help!