DG got #6. The other two seem hard so I am posting the answers.
1. Apothecary, Followers, Tournament - Each names two cards - Potion and Copper, Estate and Curse, Province and Duchy.
2. Coppersmith, Mining Village, Smithy - Each can get you a third turn Province (with Silver).
3. Bureaucrat, Harem, Navigator - These are illustrations of real people. Harem and Navigator are Valerie and Dale, and Bureaucrat is the artist, Matthias Catrein.
4. Bridge, Curse, Horn of Plenty - They all have a 0 coins symbol.
5. Ambassador, Bag of Gold, Young Witch - They each mention the supply.
6. City, Followers, Walled Village - They all relate to Carcassonne. Walled Village is a promo commemorating Carcassonne's 10th anniversary. The art for City was also used on a Carcassonne product, and Followers is what you call the meeples.
7. Black Market, Possession, Watchtower - These are the three cards with the longest FAQs. Maybe this would have been easier if Watchtower's was anywhere near as long as the other two.
8. Curse, Followers, Harem - Each has a unique combination of types - Curse, Action - Attack - Prize, and Treasure - Victory.
9. Ambassador, Fairgrounds, Mountebank - They all give you a use for Curses.
10. Counting House, Goons, Nobles - They all have the VP shield - Nobles has a normal one, Goons has it as a +1 ability for VP tokens, and Counting House has it in the art.