Florence is an extensible scalable virtual keyboard for Gnome, although it can be used on any desktop environment.
Download link : http://code.google.com/p/ardesia/
I downloaded florence-ramble_0.2-debian-1_amd64.deb and installed it using dpkg -i as root.
Could not start it and it complained about a missing libcspi.so.0.
I went to http://www.debian.org/distrib/packages and did a search at Search the contents of packages with keyword libcspi.so.0 , distribution testing.
Seemed that package libatspi1.0-0 was missing. After installing package libatspi1.0-0 Florence could be started.