nzbwolf

Offering a modern user interface this site is the best you can get out there. Finding and downloading nzb files has never been easier. The only downside is, you need to upgrade to VIP and pay with Bitcoin. There is no option for paypal or credit card payment. If you don't already have an account with nzbwolf, you should definitely give it a try.

If you are looking into adult-related content on usenet nzbwolf is the first address to go to since kleverig closed it gates for the public.

nzbgeek

Second best alternative with a great community behind it. One of the big indexers that has been there for quite a long time. Large userbase, but therefor not the fastest.

dognzb

The more glorious days of this site have passed. Back in the day it was the most reliable and loved nzb indexer out there with tons of features behind it. But today it lacks a lot of important releases in all categories, which makes it almost unusable.