Is it permissible to give Zakat to organizations that receive it to help the needy, without knowing its specific disbursement channels?

If the zakat payer takes it upon himself to distribute his zakat, and strives to place it in the hands of those who are entitled to it, there is reassurance for his heart in that. It is permissible for him to entrust it to someone he trusts to disburse it to its rightful recipients, as this constitutes cooperation in righteousness and piety.