I'm currently sending the following, interested in comments or suggestions.
I think it's probably too many links and too little analysis or actual recommendation.

Tl;dr: there are a lot of donation opportunities, a lot of people/governments donating, but I have found no clear cost-effectiveness analyses. The best article I found so far is vox.com: How you can help Ukrainians

Meta:
6 tips on disaster relief giving - The GiveWell Blog … Allow your funds to be used where most needed – even if that means they’re not used during this disaster. … The rebuilding effort can be very expensive. … It’s common for charities to use a disaster as an opportunity to raise funds for their other work. … A highly professional, experienced organization with a pre-existing presence in the affected country will likely help where it can, and stay out of the way where it can’t.
There’s already a lot of money and military support from governments and individuals, e.g. > Biden administration to push congress for $6.4 billion in aid to Ukraine - Schumer and some seem to be talking about 10 Billion.

Vox:
vox.com: How you can help Ukrainians (Also sourced from forum posts below, so beware of information cascades)

Recommended refugees orgs:

• Polish Polska Akcja Humanitarna
• Polish Association for Legal Intervention
• Polish PILNE: pomoc dla Ukrainy » Fundacja Polskie Centrum Pomocy Międzynarodowej (Ukranian partner http://r2p.org.ua/en/ )

Recommended opposition press, from a comment in the EA forum:

• Meduza (Russian online newspaper and aggregator)
• OVD-Info (Russian human rights service)

Ukrainian military:

• https://ukraine.ua/news/donate-to-the-nbu-fund/

Medical assistance:

• Red Cross [Ukrainian Red Cross https://redcross.org.ua/donate/]
• Doctors Without Borders

Polish Effective Altruism:
https://efektywnyaltruizm.org/blog/help-for-ukrainians, updated 30.03.2022, doesn’t have a lot of analysis in the post, recommends:

Military:

• National Bank of Ukraine to support the Armed Forces of Ukraine

Humanitarian aid:

• https://pomagam.pl/solidarnizukraina for humanitarian aid … has been helping Ukrainians in Poland since 2014 … will report on how they are spent
• Donate - Polska Akcja Humanitarna
• Pomoc dla Ukrainy - zbiórka charytatywna | Siepomaga.pl
• The Polish Red Cross https://pck.pl/na-pomoc-ukrainie/
• https://donate.savethechildren.org
• Ukraine Humanitarian Fund (UHF)  https://crisisrelief.un.org/t/ukraine UN fund, … As crises unfold, funds are directly and immediately made available to a wide range of partner organizations

Effective Altruism Forum:
What are effective ways to help Ukrainians right now? - EA Forum

• Comment from Nina in Kyiv links to the polish post above, adds an official bank account for medics and a broken link for the military (which I guess should be the same as this from vox) also links to three lists of charities “here, here and here”. Seconds recommendations for news inside of Russia (so Meduza and OVD-info), adds stopfake.org and informnapalm.org

Rough attempt to profile charities which support Ukrainian war relief in terms of their cost-effectiveness. - EA Forum more Polish charities with some analysis.

Others:

https://uacrisis.org/en/help-ukraine yet another list of donation opportunities

Pomoc dla Ukrainy /  Допомога для України / Support for Ukraine big spreadsheet sourcing the blog post from Polish EA linked above

The Center for High Impact Philanthropy at U Penn has posted a list: https://www.impact.upenn.edu/ukraine-crisis-how-can-i-help/

I've heard of people giving money directly through services like Airbnb. There might be something especially useful about low transaction cost giving to people in a desparate situation, who may not have much liquidity. But, I'm not really sure, just leaving this comment in case someone else has more information.