Misc DIY ideas and Fabric pros and cons
If you are using it near a fire material resistant to embers like 500 denier may be worth it especially if your primary transport is canoe/ATV or pack horse etc.:
Here is just one example but there are probably 100 more if you go looking:
http://www.rockywoods.com/Fabrics-Ki...-Retardant-ACU
Water resistant and treated with flame retardant.
All you need to know is how to sew a basic seam on a sewing machine or know someone who does.
Here are some patterns but search around and you can find many more on YT etc.:
http://diygearsupply.com/diy-guides/tarps/
A very simple symmetrical diamond tarp with cat-cut edges is fast and simple to set up but does not protect as well from strong winds with driving rain/sleet/snow like the other more complex patterns which require more guy-lines and time to set up and take down.
When not by a fire and in the summer time I like SilNylon but a small fire ember will melt a hole in this fabric.
One of several methods to make a cat-cut on a tarp, jump to minute 1:40. use this this concept regardless of what fabric you chose. Heck you could buy cheap Tyvek and glue it with super glue and/or duct-tape:
http://youtu.be/0E7Ah2KDUoU
cat-cut edges reduce all that wind flapping noise.