I agree with AG about the need to define different 'levels' of consciousness.
When we do certain things 'automatically' (eg driving along a road) we are still 'conscious' (otherwise we would veer off the first bend in the road), but that is different from being 'introspectively aware'.
My 'theory' is as follows: our brain is constantly receiving information from the external world - but most of it is pretty useless. Consciousness is a way for the brain to sort out the more important incoming information. Imagine thousands of potential thoughts/sensations/awareness competing and only a few of them reaches the conscious level at any one moment - our experience of being conscious is made by the 'winners' among the signals.
What decides which thoughts get through and which don't? That's where the intelligence of the system comes in. There are processes that 'filter out' signals that are considered to be unimportant - all done subconsciously of course. A simple example is our tendency to pay attention to rapidly changing features of the environment and ignore the constant features - ie the act of taking certain things for granted. The reason for this is most likely an evolutionary one - things that endanger our survival usually involve rapid change in the environment.
'Intelligence' should be a measure for how effective the information filtration system works. I said that the filtration is automatic and unconscious, but that's only partly true. We can also train ourselves to observe things that we normally ignore, or vice versa.
So in short, consciousness is the process of bringing filtered information to our attention, and intelligence has to do with how information is being filtered in the first place.