If my calculations are correct Diners Club points can be transferred to 36 airline programs once you allow for transfers via Starwood. 
So my current DC points balance of 120K could be converted to any of the following (including Starwood bonus for transfers of 20K):
 75,000	Aeroplan/Air Canada via Starwood
 75,000	Air Berlin via Starwood
 75,000	Air China Companion via Starwood
  1,154	Air New Zealand & Air Points via Starwood
 75,000	Alaska Airlines Mileage Plan via Starwood
 75,000	Alitalia MilleMiglia via Starwood
 75,000	All Nippon Airways (ANA) Mileage Club via Starwood
 75,000	American Airlines Aadvantage via Starwood
 75,000	Asia Miles via Starwood
 75,000	Asiana Airlines via Starwood
 75,000	British Airways Executive Club via Starwood
 75,000	China Eastern Airlines via Starwood
 75,000	China Southern Airlines’ Sky Pearl Club via Starwood
 75,000	Delta Air Lines SkyMiles via Starwood
  1,000	EL AL Israel Airlines - Matmid Club
 75,000	Emirates Skywards via Starwood
 75,000	Etihad Airways via Starwood
 75,000	Flying Blue via Starwood
 30,000	Frontier Airlines -*EarlyReturns
 75,000	Hawaiian Airlines via Starwood
 75,000	Japan Airlines (JAL) Mileage Bank via Starwood
 60,000	Korean Air - Skypass
150,000	LAN LANPASS via Starwood
 75,000	Miles and More via Starwood
 75,000	Qatar Airways via Starwood
 30,000	SAS (Scandinavian Airlines) - EuroBonus Points*
 75,000	Saudi Arabian Airlines Alfursan via Starwood
 75,000	Singapore Airlines KrisFlyer via Starwood
 60,000	South African Airlines - Voyager
 30,000	Southwest Airlines - Rapid Rewards
 75,000	Thai Airways International Royal Orchid Plus via Starwood
 37,500	United Mileage Plus via Starwood
 75,000	US Airways Dividend Miles via Starwood
 37,500	VARIG Smiles via Starwood
120,000	Velocity
 75,000	Virgin Atlantic Flying Club via Starwood
Alternatively 120K DC points would get me the following hotel points:
118,800	Best Western Rewards (plus a few DC points left over)
120,000	Choice Hotels - Privileges Points
150,000	Hilton Honours via Starwood to Hawaiian Air or Virgin Atlantic
 60,000	Hyatt Gold Passport
 60,000	IHG | Priority Club*Rewards
 60,000	Marriott Rewards
 60,000	Starwood Preferred Guest
Now to work out which would be best for me. Might be a long job as half of these I have never heard of!