I use my seal a meal to reduce the size/bulk of fabric I'm shipping. They work like the space bags. You will be surprised at the amount of fabric you can ship in one of the boxes or envelopes you get from the post office. Also, it's cheaper to ship in a box or envelope from the post office than other types of boxes or envelopes.

there is an advantage to using the priority boxes/envelopes & that is that they come with 50$ of free insurance and a tracking #...it's also a lot cheaper this way if i ship something west of the Mississippi River -- otherwise it is very costly!
[i am in PA]

I used a regular trash bag and sucked the air out with the sweeper hose and twisted it and it worked. Took a quilt on the plane and fluffed it in the dryer when I arrived. Worked great. Vi

Shipping is cheaper than driving it or going to pick up yourself...and quicker. We pay for services.
sandy

I ship using USPS priority boxes using Pay Pal. You get the same discount as on USPS. The advantage is when you ship an item less than 13 ounces that can go first class package rates. You get a tracking info for 19 cents and discount rates that the USPS doesn't offer. Free pickup is the bonus!

I send a lot of items by priority. You can buy extra large Ziploc bags and squeeze all the air out. Cheaper than space bags and send priority also. They come in 4 packs for about $5-6.

Have done this also. Works great for extra packing insulation so things don't break.

If you have your dimensions and weight you can also price compare on-line with the different shipping companies to see who might have the best deal for what/where you are shipping.

If one does a lot of mailing/shipping, a scale that weighs in fractions of ounces is worth buying. Some are also known as diet or kitchen scales.

If you're shipping donations, take to the group you are making them for. They might have a lot of stuff going to the same place, and yours could go too. Just a thought.