In Here There Be Monsters, by Andy Lane, the First Doctor, Susan, Ian and Barbara arrive on a strange spaceship run by a vegetable alien which is punching holes in space. Carole Ann Ford does a decent Hartnell, and the story is excellent.
The Great Space Elevator, by Jonathan Morris, is the best of this run (though they are all good). It is a delightful homage to Season Five, with elements from almost all of the Victoria stories (and elsewhere from the Second Doctor's time) shaken together to form a very entertaining mixture. I think you could use this as a good entry point to the whole Companion Chronicles for a Who fan otherwise unfamiliar with the audios.
Marc Platt's The Doll of Death is literally the first decent Third Doctor audio I have heard (and I include also The Ghosts of N-Space and Paradise of Death among those I didn't like. As you would expect from Platt, he takes the story very much towards the surreal, with two literally contraflowing timestreams. Manning does lots of male voices well, and the plot is inevitably a bit confusing but avoids being self-indulgent.
In Empathy Games, Nigel Fairs continues his line of flashbacks from the point of view of post-Gallifrey Leela, defiantly enduring her fate. Here she remembers an adventure where she became a fighter in a local violent hunting event - Chris Boucher, her creator, also wrote this basic plot for her in Last Man Standing, but Fairs does it much better, because i) he isn't trying to be satirical, ii) he writes the Doctor better and iii) he benefits from Louise Jameson's excellent delivery. It is perhaps my least favourite of the four, but as I said they are all good.
All of these are recommended.