Here is a talk and the presentation slides about how to optimize texture transferts in OpenGL. The presentation covers textures uploads in multithreaded applications, PBOs and synchronization (GL_ARB_sync). The talk is available HERE. You can download the presentation PDF HERE.
This presentation is also available in OpenGL Insights, a new OpenGL book, under the chapter Fermi Asynchronous Texture Transferts:
For an overview of the contents, just visit this link.