I impressed even myself when I was able to pack for 5 days at the beach (including formalwear and a cocktail dress) and 3 days at a ski resort in just one carry-on bag. I did it by compressing my snowboarding outfit in a luggage ziplock bag. It doesn't require a vacuum, just stuff it with bulky clothes, partially seal the top, then press out all the air and finish sealing the bag. I do this by putting the bag on the floor and kneeling on it to use my legs to get it as flat as possible while sealing it up. It doesn't help to reduce the weight of clothes, of course, so it's a relatively heavy thin package. And it doesn't help particularly much with already-thin clothes. But I almost always use it in winter with sweaters, ski jackets, etc. I got mine at LLBean and have been using the same bags for years, although there are other brands available in stores.
