Jags, a further note on tarps, following Dan's very comprehensive note above: A lot depends on bugs, their numbers & savagery, and one's own tolerance. Since I live close to & do a lot of camping on the Canadian Shield, I have to take account of bugs, so that limits the use of tarps. They're always great as shelters against wind, sun and rain, but without a quality inner shelter against bugs (blackflies especially, but also mozzies) in these parts they're limited as a primary shelter to spring, early summer, and later summer/autumn. Here, the best summer months--June, July, and the first half of August, are also high season for bugs. (There are some people who ignore blackflies, but I'm not one of them.)
As an indicator of what's available in tarps, here's the link to the MEC catalogue:
http://www.mec.ca/shop/camping-tarps-and-light-shelters/50130+50712/?h=10+50055+50130Of the ones shown here, I have two rectangular Integral Designs Siltarps, large & small. They're very light (small one is just 400 gms), well made, handy, and I use them a lot. Trees, etc., are obviously best for rigging, but I've found that a combination of a tent inner, plus an upright bicycle, works pretty well too. Rigging requires a bungee cord or two, light braided nylon cord, and I also use the indispensable quick-release rubber ties I get from Lee Valley Tools, in different lengths.
Some of the newer one-person tents, esp just the inners, are almost as light as a bivy sack, and more spacious. Recently, I've done some arithmetic on the various combinations of my tents and tarps. Happy to share those figures if you're interested -- send me a P/Message if so. FWIW, I'm tilting towards a Tarptent DW Moment as (for me) the most versatile combination of weight-weather protection-bug protection-reasonable 3-season durability. Not the absolute lightest, but easier to use than buying/using separate bits & pieces in various combinations. My research is telling me, however, that lightness ain't cheap -- "less" is certainly more...
Cheers, John
PS: Bought my Wenger Swiss Army knives from Knifecountryusa.com -- check it out, there's a whole other world out there...