If I remember rightly all the Nazgul were fighting at Gondor, so is there any hint of who may have led the forces of Dol Guldur?
There's no indication of who led the attacks on Lórien; all that is recorded is "First assault on Lórien", "Second assault on Lórien" and "Third assault on Lórien", as well as a slightly longer text in the Tale of Years:
Three times Lórien had been assailed from Dol Guldur, but besides the valour of the elven people of that land, the power that dwelt there was too great for any to overcome, unless Sauron had come there himself.
Regarding Mirkwood, there is likewise no record. We have this:
Battle under the trees in Mirkwood; Thranduil repels the forces of Dol Guldur.
The realm of Thranduil was invaded, and there was long battle under the trees and great ruin of fire; but in the end Thranduil had the victory.
However, there is actually no indication in the text of Return of the King that all of the Nazgul were involved in the Siege of Gondor. All the textual references are to "the Nazgul" or "the Ringwraiths", but there is no mention of counts or numbers.
We know that the second in command of the Nazgul (Khamul, the Black Easterling) was in charge of Dol Guldur, and that he had two other Nazgul with him there, and so it's just as likely that it was him and the others who led these forces.
The other main battle in the north was the Battle of Dale, and the hostile force in that was Easterlings:
It lasted three days, but in the end both King Brand and King Dáin Ironfoot were slain, and the Easterlings had the victory.
Presumably these were led by Easterling chieftains.
Tolkien rarely goes in to great detail when describing Sauron's forces in Middle Earth, aside from several enemy commanders in the most chief conflicts. Most of these battles are mentioned in a matter-of-fact manner citing the efforts of the free peoples and the end result. Like the other answers to your question, Sauron had many underlings. The enemy commander could have been an orc, an easterling(maybe even a sorcerer), possibly one of the Nazgûl or even a lesser wraith serving under them. None of the sources which are the Tale of Years(found as Appendix B in the back of the Return of the King), and, based upon it, The Atlas of Middle Earth by Karen Fonstad, mention the identity of the enemy commander. But we have to assume there was one.