The "Heaven for Everyone - Roger vocal" started me off on a path of finding Roger singing songs previously sung by Freddie on solo ventures.
What about Brian? There is the obvious stuff on "Live at Brixton Academy" but I have never heard any tracks from the "Another World Tour".
link
Unfortunately it's not really good quality (there's another show on Maki's site - Hamburg '98 - which is in much better quality, but it's offline at the moment). Brian sings a bunch of Queen songs here. Spot the solo on FBG's and you get a special prize ;)
V.
Songs I've heard Brian sing live (That Freddie normally sings)
Now I'm Here
In The Lap of the Gods...Revisited
Bohemian Rhapsody
Tie your Mother Down
Somebody To Love
Teo Torriatte
We Will Rock You
We Are The Champions
Mustapha
Fat bottomed Girls
Tear It Up
Hammer To Fall
Headlong