The most trustable things:

Redns0w for tethered jailbreaks on iOS 6(or untethered on iOS 5),downgrades to IOS 5 or below and some other handy stuff.This includes baseband managing;

Evasi0n for iOS 6.0 through 6.1.2 untethred jailbreak;

sn0wbreeze for untethered jailbreaks on untethered jailbreak suported firmwares,including the old bootrom 3GS downgrade,also for SHSH blobs managing and creating custom firmware for downgrade.This includes baseband managing;