Depends on your situation but I will give you absolute mininums:
FHA - 580
VA - 620
Conventional - 620
Jumbo - 680
Now once in these programs, the higher the score the better the rate. So for example if you go Conventional at 620, for the better rate you need 720+. There are also tiers for rates. For example from 620-639, a different rate, 640-659, a different rate, etc. Hope this helps.