It's looking more and more likely that Sony's new handheld, currently known as the NGP, may soon receive "PS Vita" as its official name. The source code on Sony's own E3 2011 contains a handful of references to the name, including two subdirectories apparently labeled "Games and Media" and "Features." Attempts to access either subdirectory leads to "page not found" errors for the moment.
This is the second time the name has been discovered on one of Sony's own websites, having previously been spotted on the SCE developer site. Again, it's possible that Sony is simply using an internal codename for the device, though evidence to the contrary is certainly starting to add up.