The ones you have shown look pretty even, just that the edges are a little ragged. I'd probably press them well with spray starch/size then trim them up as close to square and the size you want.
If block sizes are different, but not too much, you might be able to equal them out by some seams being slightly wider/narrower. Watch though, where you have points and would cut them off.
As the others have suggested, sashing will help you get things further squared up, though I'd start first with what I have suggested.
Of course, depending on how many blocks you have and what size of quilt you are trying to get to ... I'd consider doing groups of blocks, rather than sashing with every block, as the ones you have shown don't look like they are too big.