try this website
http://blog.iphone-dev.org/post/126908912/redsn0w-in-june

this is the dev team's website they are the ones who put out programmes like redsnow,ultrasnow,pawnagetool and quickpawn.....

and 3.1 has been unlocked by them but it is a complicated process and u might brick ur phone in the process

so better stick to the firmware version 3.0 and unlock it

they have detailed instructions and firmwares in the website mentioned above
hope this helps