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Stock and Futures Price Feeds and API's

I'm researching stock and futures price feeds and API's to try and determine what features the different feeds have and see if anyone else out there has had experience with any of them...?

I've come across a feed by DTN called NxCore. So far I haven't been able to work out if it's the same as their IQFeed. Anyone know? Here is a PDF explaining it:

Anyone ever used the API provided by eSignal?

Does TradeStation provide a price feed API?

Any others...?
Thanks pt - that's the sort of thing I'm looking for. Have you ever used it? Or know anyone that has?
open ecry provide excel API, if you are good with excel then basically you have all future charts for free.
Thanks nkhoi.