I have a hammock, but I've always found it too cold in anything other than mid-summer. It is great then though – super comfortable.
Other times, I just use a MacPac waterproof sleeping bag. Cost a lot (I got my two for £150 and £180, one in a half price sale and the other at a very big (30%ish) discount). The summer one I have is about 500g, and that is all you need to take for an overnight camp. The winter one is closer to 800g, and if it is really cold, you need a camping mat. Whichever way, at 500g for summer, 800g for autumn, and about 1200 for proper winter, it is by far the lightest full sleeping solution, if nowhere near as comfy as a fancy hammock will be.
Oh yeah, and it is tiny, in summer I can ride and camp out with just a 20l camelbak bag (I have one of the walking/climbing ones), and nothing strapped to the bike. Makes the riding more fun.
Only problem is MacPac have stopped making their waterproof sleeping bags, so I don't know who makes them any more. Probably adventure race types would know – that is who they were originally designed for.
Joe