“Trinity” will allow you to install custom software onto your Vita, even at the highest firmware version 3.70. Enter at your own risk.
“Modoru” is a new tool for hacking the PS Vita which allows you to roll back to any version of firmware for the handheld. This opens up homebrew for everyone!
PS Vita had been touted as unhackable by Sony, in no small part due to its proprietary data storage cards.