Various Catholic agencies are collecting donations to aid with the humanitarian crisis in Ukraine, as people flee to escape Russian bombing and shelling. Here are some places to donate. This list is not exhaustive.
The international Caritas confederation is collecting funds to help Caritas Ukraine. In the United States, that is through Catholic Relief Services: https://bit.ly/3LWtOKa. Internationally, you can donate through https://www.caritas.org/.
The Ukrainian Catholic Archeparchy of Philadelphia also has a link: https://ukrarcheparchy.us/donate.
Two pontifical agencies also are taking donations for Ukraine: Catholic Near East Welfare Association, https://cnewa.org/campaigns/ukraine/, and Aid to the Church in Need, https://bit.ly/3sgpuNV. Internationally, Aid to the Church can be reached at https://bit.ly/3vfqCn4.