Popular GTA IV modding tool OpenIV has finally reached a 1.0 release today. The main new addition in this update by GooD-NTS and the rest of the team is support for opening and viewing Max Payne 3 textures and collision bounds objects.
Other changes in this release include:
new texture viewer
improved GTA IV vehicle rendering
simple text-based format for easy WPL editing
many other improvements and bug fixes
The video below demonstrates some of the tool's features. Download links after the video.