On my Giant Rainier - 17" (TopTube length = 22.64").
On my new Titus Racer-X - Medium, which is 19" (TopTube length = 23.25").
Their standover heights are both around 29.75"
I'm 5'8" which seems to be a height where I can go either small or medium frame on most bikes.
The fit on Rainier gives me a little more of upright position than the Titus. On Titus, a smaller frame might have been more appropriate for me as I am at the bottom range for a medium, 5'8" - 5'11", but I found a great deal on a medium frame and I couldn't pass it up.