Earlier today (Monday), Apple released iOS 4.3.5, a security update that patches a flaw in its handling of security certificates. If you're looking to jailbreak 4.3.5, though, here's some good news: "MuscleNerd" of the iPhone Dev Team decided he would check to see if Redsn0w would successfully jailbreak the minor update. You can, however there are still a few pitfalls.
First, the jailbreak only works with the iPhone 3GS, iPhone 4, third- and fourth-generation iPod Touch, and original iPad. (Sorry iPad 2 owners; you're out of luck. Again.) Also, this jailbreak is only limited to a tethered boot with iOS 4.3.5, so whenever you reboot your iDevice, you will need to connect it up to your computer. Lastly, you can't use Redsn0w if you use a carrier unlock.
iOS 4.3.5 is Apple's second security update to iOS in the last week and a half or so--Apple released iOS 4.3.4 on July 15, which fixed the flaw that Jailbreak.me 3.0 took advantage of.
If you're on iOS 4.3.5 and are willing to give this a try, you can download the necessary files for Redsn0w and then following the steps on Redmond Pie's website.