I've had these experiences too, though none that necessarily link to anything in particular. I'm just sensitive to noticing serendipidous events.
There are, of course, several ways to look at these, and some have been touched on already, but it seems to me this thread boils down to, if we had to put it in question form, is "If it means anything, what does it (or could it) mean?"
With that posed, this is what I'm seeing:
One could take the stance that it means something, or that that it doesn't.
If one takes the stance that it doesn't, then that person has to answer why they occur, to which he or she would probably respond with what has been responded with here - our mind notices certain things regardless, and we program ourselves to notice certain things regardless. At that point, yes, noticing many coincidences during the course of a day just means that you are exceptionally tuned in to "your world."
That is, you are more likely than others to notice on a conscious level the patterns you see, events that take place, colors, people, conversations, etc and because you've been "programing" yourself to see coincidences on a conscious level since you were little, you are thus more likely to notice coincidences than those around you. You probably are just as able to pick up on coincidences in others' lives as you are to pick up on them in your own because for you every little thing that happens may be imporant later - you subconsciously choose to remember it, which means you can link to it later when something similar enough happens.
A person from this point of view would probably also point out that not *everything* that could include an 11 (for example) in your life, does. It appears you were not born on the eleventh of a month, and based on not mentioning it, you probably were not born in the eleventh month, or hour of a day, though chances are (because we are great at finding correlations), something about your birth involves the number 11 (something divides evenly by it, there were 11 people waiting, two other numbers involved add up to it, you took a mere 11 seconds to shoot out of the womb, your mom had taken 11 breaths just before you were officially born, etc). Unfortunately, you were a wee bit too young to have really started taking note of patterns yet.
What I think is interesting about this viewpoint is that so often it's made out to seem like a bad thing that a person is noticing these coincidences...my suspicion is that it mostly means a different psychology, and those same skills developed by noticing those patterns are useful for other things! From this point of view, as long as one recognizes that this is all it is (well, "this" still being fairly complicated), then continuing to see those patterns is not going to take over one's life or cause one to become obsessed with pi, etc. But that's a sidenote.
All of that make sense? I'm never sure what I'm writing does :p
Of course...there is the other end: That it *does* mean something. If a person takes this view, then one has to come from some sort of base which would allow the coinidences to mean something.
For example, a belief in certain sorts of god(s) would allow these coincidences to mean, potentially, that you are seeing a sort of "hidden" aspect of divinity. That is, you are seeing more clearly than others the underlying workings of the universe, so to speak.
I had intended to go into more on this side of the argument, since it has thus far been underrepresented, but apparently the football game for today has started and I'm required to watch it. Le sigh.
But then, looking at how much I've typed already, it's probably a pretty fortunate coincidence for everyone that I have to watch football