Here in the UK we have a show called "Mastermind" in which people choose their "expert" category about which the host can ask them anything, and then a general knowledge round. One of my dinner party questions is asking people what their Mastermind category would be. (Mine would be the life and work of Michael Crawford, but that's niche enough not to be helpful to a lot of writers ;)
Anyway, I'm American but have lived in Scotland for 10 years, so can answer questions from both an inside and outside perspective. I'm a Byzantine history buff and have read the Bible through several times.
My current WIP has a brainy but severely dyslexic MC and I need some info on coping and compensating strategies, what sort of work he'd be able to do, and how dyslexia changes someone's perspective.
This 'expert' thing is a great idea for a board topic :)