iOS 4 was released 5 days ago, but that didn’t stop Cydia developers who immediately started working on compatibility fixes for their apps and tweaks. Yes, iOS 4 is jailbreakable, in case you’re still wondering.
Three popular apps have been updated this week for iOS 4 compatibility: Winterboard (the theming tool from Saurik), Backgrounder (the good old tweak that enabled multitasking way before iOS 4) and BTStack GPS (to pair your iPhone with an external GPS device). You can find Winterboard and BTStack GPS in Cydia, but if you want to install the first version of Backgrounder for iOS 4 you’ll have to do it manually.
Go download this .deb package, move it via SSH to /var/mobile/ and install it using iFile (from Cydia). Like I said, it’s first alpha version - pay attention to bugs and slowdowns.