Clear plastic lettuce and salad containers from the produce section. I use them to sort my scraps as I cut them into different sizes. Sure saved a lot of time when I needed a quick baby quilt. And when I had a bunch of different sized pieces that I had to keep corralled for a top, out came those containers. I just set them in order on top of my counter and the pattern became very manageable.

I use my digital camera to keep me on track. I lay all my blocks and sashing or what ever is involved in rows of my quilt. I than take pictures of how it is laid out. I use to put row markers but they seem to fall off or get lost in the handling. This way, when I lay it back out I check my camera and can lay it back to the correct way real easy , no guessing and no time lost... When all finished I just delete the pictures and I am one less stressed, very happy Quilter.

I bought a long pair of scissor-like clamps at Harbour freight. Great for turning things inside out and pushing out points. Also handy for picking up things I drop on the floor. I use those 4 pair pant hangers for hanging UFO's and my collection of seasonal mini quilts. And I know many have them but no on mentioned the magnetic nut and bolt dish from Harbour Freight for pins. I love how the pins jump up to the edge. Makes them easy to grab.

One of the best reuses of a tool I have is a thin bladed paring knife. When I have to rip a lot of long straight seams, I insert the pointy tip into the seam and just slide it along. It cuts those stitches so fast as it flies along the seams, and the thin blade stays right in the folded hem.
This works best on deconstructing linens, etc. but is good on almost any straight seam.

I am also a dedicated user of the clear plastic produce containers.

I keep a group of small paintbrushes, and a few "proxa" brushes near my machine for cleaning in and around the bobbin race. Gets all the lint and easy to clean, just run them through the thin teeth on a comb and no damage or expensive repair bills.

I use a telescoping wand magnet, a mechanic's magnetic bowl when I'm working on old sewing machines. Also a lint roller for picking up threads and such from my cutting mat.

I had to look at the new suggestions -- you folks have great ideas!!

Here some more I noticed when I was sewing today:
-- plastic boxes that are for storing the scrap book paper - they hold my finished blocks, the layer cakes, folded 2.5" strips, etc.
-- Coffee cup used as a holder for thread spools
-- small plastic hair claw clips -- I use these as extra thread guides when I use an external thread holder
-- sticky notes -- a stack marks the seam allowance, the extra sticky ones can attach to pieces, blocks or rows so I can write notes
-- laminator -- I laminate my most used patterns so they don't get munged when I use them over and over
-- I second using blue tape -- it is great for marking the quilt for straight line quilting and helps hold things in place without ruining them (if I can keep DSiL and DH from borrowing it). I keep an assortment of widths in my sewing room.

Keep the ideas coming ladies!!

I had to look up thread nets, I didn't know what they were. Great use on condoms! They sell cheap ones at the dollar store.

i LOVE ALL MY TOOLS! THE OLD AND THE NEW<3<3<3

I save my old prescription bottles. If you wave the hot air from a hairdryer over the label for about 30 seconds, you can peel the label right off, glue and all. Comes off cleanly. Then I use those bottles for a variety of things, such as buttons, safety pins, to dispose of broken needles, etc...