OK, I keep finding bits and pieces of how people are shocked at the price of fabric and how to continue to build their stashes despite it. I thought a post where everyone shared their tricks and techniques to still affording to build their stashes would be helpful especially in this dry economic time.
I will go first.

1. I seek out ESTATE SALES and get there when they open the first day.
2. I always look at all garage sales and ask as soon as I arrive if there is any fabric. I go directly to that location first.
3. At each new quilt store I visit, I ask for their ON SALE fabric upon arrival and find goodies there.
4. I too have begun to cut up old cotton clothing
5. I seek daily on CL for fabric sales - people selling their stashes at only $1-2 per yard. Most are $2 per yard and they have a great selection.
6. I buy from folks selling their stash in bulk and ask if I do that ahead of time if they will also cut me an additional amount depending on how much I buy.
7. Lastly, I sell items I no longer use or need to build up my stash spending money. This has proven to be very helpful and then I have cash when the right time arises.

I am very curious to know what everyone else is doing to build that stash. Please share!

Sale shopping, and like you thriftstores, yard sales and other online sources.
I also have spread the word to my family to save cotton clothing, especially jeans :D:D:D

I do all the above.. My family even keeps a look out for fabric and notions for me when they go garage sale-ing and or flea market-ing..

I'm still trying to use more of mine up :)

I have 2 close girlfriends with HUGE stashes so I "shop" there :) :) :) I can usually find what I'm looking for and I purchase it at a discount. Also my DD's sister-in-law is an interior decorator so we get her scraps/samples/left overs for crazy quilting.

Wow... that must be sweet. They must have a huge area
filled with treasures.

I am very careful in cutting fabrics and avoiding waste. That's the biggest thing for me. I don't keep the tiny pieces of scrap, but I try really hard to avoid waste otherwise. That goes for buttons, zippers, etc. Everything in the studio is worth $$$ if I have to replace it. I also cut up clothing that is in very good condition and salvage buttons, zippers, hook and eyes, and so on. Same with purses. Since I like to make purses for my etsy shop, I know the cost of purse components. I try not to purchase any notions for purses I make for family and friends (especially if they aren't paying).

One of my friends has a 2 car garage, dining room, and Florida room (den) full of fabrics. The other one has an entire bedroom filled with fabrics.

This is an excellent point that you made about not wasting here Fluer.
I too cut off buttons and even save well made collars. I have used double sewn collars for all sorts of bands and such for husbands needs in wearing a night lamp when walking dogs or other things. Reusing all the parts of fabric and clothing and they notions they hold is an excellent way of recycling "Down to the Bone" if you will.
I also am a very thrifty cutter when quilting and sewing. I waste only the absolute amount necessary to get great cuts but preserve as much as I can. I am so bad that as I have been cutting 100's of apple cores out for a charm quilt, I even look at the itty bitty scraps and wonder... Can't I use this in some way and then laugh. we are talking smidgens of fabrics. LOL

Thrift stores for cotton curtains, bed sheets, clothing. Sale/Clearance/remnant sections at the fabric shops and craft stores. I'm also careful about not wasting while cutting. And have found some bargains on ebay as well.