Earlier today, Qt Software released updates to Qt and Qt Creator. Both releases are available for download from http://qtsoftware.com/downloads -- either stand-alone or as part of a new build of the Qt SDK.
Qt 4.5.1 includes bugfixes and optimizations made since the release of Qt 4.5.0.
Qt Creator 1.1 incorporates a good deal of user feedback gathered since the 1.0 release, and provides a broad collection of improvements and additions.
For more details on the releases, check out the recent posts at Qt Labs at http://labs.trolltech.com.