There's apparently a Yak-40 being developed in the Russian FlightGear forum - and the first post in
this (Google Translated) thread links to a Yak-40 for FlightGear being hosted on Google Code.
I'll check it out and see if it's any good.
Here's the main page if anyone is interested.Update: Just flew with the non-SVN version for a bit and holy crap it sucks; you practically need to put thrust to 80% to taxi, it makes the Tu-154B's sounds and you can't even steer it without using the rudder while in the air
trying out the SVN version...
Update 2: Not gonna bother with the SVN version either, it's basically the same plane except that you can steer it in the air with the ailerons rather than the rudder. But other than that, it's the same thing.