Ask HN: What are good genealogy/family history/immigration search engines?

I recently came across some family names that I was previously unaware of. Some family members had been separated, killed, or went missing during WW2. Are there good places to search for records, especially those from Germany, Ukraine and Russia? I'd be especially grateful for some sort of adoption records from Germany from the mid/late 1940's. Also wonderful would be birth/death records.