I'm not sure exactly how to answer - there's only one person I would count as an actual close, personal friend who I talk to on a regular basis.
Other than that, I could name 20+ I've met / known briefly / used to know / et cetera.
Also, I think it's worth mentioning that people might actually know a trans*person without knowing it or directly realising it. Some trans*people aren't "out" or vocal about it. If a person can and is trying to "pass", you might never know they're "different" unless you see them naked (and sometimes not even then).
There's a local teacher who is trans* near me, and you wouldn't know if she kept it secret (she has a website and everything aimed at informing and helping others, so it is definitely not a secret).
There are lots of trans*people who prefer not to be "out" (or for whom it would be dangerous), just wanting to live normal lives. You might know them without actually knowing it.