THE RAVEN - 4x06 - 3/5
I get the impression this was supposed to be Seven's first major character focus episode, but it spends too long setting her up for going crazy and leaving the ship, that not much time is left for exploring The Raven and resolving the episode. As such it's a little on the dull side but a good development and background for Seven nonetheless.
There was also something nifty about seeing a Federation ship crash landed in the Delta Quadrant, although it raises a great deal of questions as to how it got to there in the first place. Did the Borg drag it there and THEN assimilate them? Was it in tow for while as they assimilated the technology and then discarded it?
Anyway, if memory serves, I believe this gets covered later on so I'll leave the pondering for now.