There are many different groups of "Old Believers". It's more proper to call the majority of them "Old Ritualists" since, for the most part, their theology is completely Orthodox. Though in some of the more secluded groups, superstition has equal weight to actual Orthodox teachings. They are split up into two main groups, the "Popovtsy" or "Priested" and the "Bezpopovtsy" or "Priestless". Both are split into dozens of other groups, and all but a few are uncononical. There is a parish in ROCOR in the US, and dozens of "Edinoverie" parishes in Russia, who are directly under the Moscow Patriarchate, whose Bishop I believe is Yuvenal of Kolomensk.
Edinoverie - Wikipedia, the free encyclopedia