Not watching but listening to...
Some of the "Lost Stories" Big Finish Doctor Who stories (audio adaptations of stories that were nearly made for the TV show but then fell through).
The Nightmare Fair (possibly the most famous missing story, set to be the first story of Colin Baker's second season and just weeks away from production when the whole season got canned
). Great fun. It's something of a pity they didn't choose to do these earlier, though, as they inevitably had to recast Michael Gough.
Not the greatest story ever but a lot of fun and a shame it didn't get made.
Mission to Magnus on the other hand... listened to about 20 minutes and turned it off. What crap!
Happily I'm halfway through Leviathan and that is absolutely excellent so far. The Doctor and Peri land in a medieval village where the mythical Herne the Hunter is all too real and has the locals running for their lives. Fantastic story so far with an awesome cliffhanger and I've still no idea WTF is going on!