No, you can call up to 10 subsequent future calls from 1 single transaction (apex invocation from a class/trigger/webservice), although you can't call a future method within a future method. So you can't have a trigger for an example that will call some future method, and inside that method calling another future method.
I guess in your case you're trying to do another future callout from within the method that is already annotated as @future and it's being called from another class/trigger?
Here you can find more information around the governor limits, and also the Limits class which you can utilise to get the number of methods with the future annotation that have been executed (Limits.getFutureCalls())