Below is a listing of the market data sources (data feeds) that Investor/RT currently supports, along with contact information and Internet addresses.  The sources highlighted in blue are brokerage feeds. DTN Market Access can be used for historical data with any of these.
  

Data Service	Timeliness of Quotes	Phone Number	Additional Information
DTN IQFeed Windows DTN.IQ Windows or Mac OS X	real-time, delayed, or end-of-day	800.475.4755	More About DTN IQFeed
eSignal Windows	real-time, delayed, or end-of-day	800.815.8256	More about eSignal
DTN Market Access Windows or Mac OS X	non-streaming intra-day or end-of day (backfill only)	800.475.4755	More About DTN Market Access
OEC Windows	real-time futures	OEC Clearing Brokerages	Requires MarketDelta Trader Software
CQG Windows	real-time futures	AMP Clearing Brokerages	Requires MarketDelta Trader Software
Zen-Fire Windows	real-time futures	Live Support	More About Zen-Fire
Rithmic Windows	real-time futures	Rithmic Brokerages	More About Rithmic
Optimus Windows	real-time futures	800.771.6748	More About Optimus
Infinity Futures Windows	real-time futures	312.373.6220	More About Infinity
TransAct Futures Windows	real-time futures	877.872.3303	More About TransAct
Interactive Brokers Windows or Mac OS X	real-time	877.442.2757	More about Interactive Brokers
Yahoo! Finance Windows or Mac OS X	end-of-day daily data only	NA	More About Yahoo! Finance