If you want really light you can't beat the abetta endurance. Don't have to worry about taking care of leather as well. Comfy, fits well, and you don't cry when it gets wet or muddy. Cheap-but then again won't last as long as a leather saddle. But mines been going for two years with no issues.
We have two of these now. Just check the nylon rigging before heading out. I got my bf his used for 150 off craigslist and it was in perfect shape. We have the one with the aireride(think thats what its called),not the fleece bottom.
If you want something leather there are some circle y endurance
[ame="http://www.amazon.com/Flex-Lite-Endurance-Expedition-Saddle-Circle/dp/B000XMX0DE"]Amazon.com: Flex-Lite Trail Endurance 'Expedition' Saddle by Circle Y 1575: Sports & Outdoors[/ame]
that is a flex but they are not all. I do really like some circle ys.
and tucker endurance
But they are much heavier.