Requires iOS 4.2
Does NOT work on 4.3 or higher
This tweak lets you ignore updates in the App Store. You slide down the Updates' tableview to toggle editing mode, and then select them (see the Video Demo below)
This only blocks the current version of the update, if you block update v1.1 of an app, when v1.2 is released it will show up unblocked. So far there is no way to unblock.
Link for Screenshots is further below.