LossLess texture compression

Is there any way for OpenGL to perform lossless texture compression?

Not that I know… But there is a very nice algorithm to perform compression with no noticeable visual quality loss. Check http://developer.nvidia.com/object/real-time-ycocg-dxt-compression.html

I tried this technique a year ago and I was very impressed, because ther was no noticeable quality loss. It requires some shader power, but that is neglectable on modern GPUs.