I would like to do spme simple projects, and am wondering for a good source to explain and compare camping fabrics.

Idea 1) i would like to make a simple and ultra light rain kilt. Some loops on the corners and it could double as a wind break under the hammock, or a ground cloth. (Too small to be an emergency tarp.)

Idea 1a) make an ultra light rain poncho.

Idea 2) making some stuff/compression sacks.

Idea 3) is really cool as a luxury for an ounce weenie. I might try and make and sell this one for fun...

Have you taken a look at ripstopbytheroll.com? I've used them for all my DIY hammock stuff and have had pretty good service. There's even an option to order samples on the site.

The owner, Kyle, is pretty active on the hammockforums websites. He seems pretty nice and willing to answer any questions. I'll confess that I've not spoke directly with him though.

There have been better explanations in the past regarding mat'ls than I am seeing now on a search. I see what you are asking for though and can only say that for a kilt you may want to go with something that is not waterproof, but has a DWR (Durable water resistant finish). Something like that shouldn't be waterproof.

Regarding stuff sacks - I always choose silnylon (at least sil coated on the inside) because things slide in and out so easily. If sil on both sides then it also slides into the pack more easily. Choose a light color so you can see down into the sack. You can make a waterproof model with a roll down closure quite easily, or make one with a double drawstring (one several inches below the other) to create a good seal.

+1 on RSBTR. Kyle runs a good cottage distributor for home DIY folks.
I've gotten materials from Dutch, too and have been very happy.

Standard 1.1oz silnylon will be the best and most available light waterproof material out there. Silpoly is similar but with much less stretch when wet. Like Portagekeeper said, these silicone impregnated fabrics are extremely waterproof, but do not breathe at all and will also trap moisture inside if you wear them. There are nylons just as light, or even heavier with DWR finish that might be better for a wearable garment or something enclosed, like a tent liner.

I love making stuffsacks out of Sil scraps. Buy a bunch of shock cord and cord locks and go to town outfitting all your gear with new sacks. They are light and durable and water proof except for seams and closure. If you wanted you could seal the seams and make waterproof roll-tops too. Thru-Hiker has a pretty good instructions.

A project popular with ultra-lighters is a dual purpose rain poncho/tarp made from silnylon. I've never tried it.

Other simple projects as long as you mention the hammock:

Tarp Snakeskins out of NoSeeuUm Mesh.
Double-ended stuffsack for hammock/quilts or tarp.
Hammock ridgeline organizer for headlamp/knife/etc. Mesh also works well.
Fronky-style Bugnet out of noSeeUm mesh.

I've found all of these to be pretty easy to make and they all perform really well out in the woods.