After finding one in a hardware store, I found I could just sit still at around dusk and be able to enjoy their visits
from a few feet away.
This picture unfortunately was a little out of focus. I also find that it's a very popular
spot when it's raining.
This guy was almost always
on his perch
where he can swoop in to drink and also keep an eye out
for intruders and possible mates.
I caught this one through the screen, as you can tell (the screen was about invisible until the flash went off), as he's dive-bombing an intruder and driving him off (the intruder is gone -- they move fast!) 
Click on any picture for a larger version.
This evening
I counted at least three, I think there were two males and one female. If I see that they mate and build a nest in the maple tree, I'm sure the camera and I will be climbing ... can you imagine how small the eggs are? Although, this late in the season, it could just be the females and fledglings
are both out of the nests.
For more information on Ruby Throated Hummingbirds go to Operation Rubythroat.