I'm a very big fan of the Eagle Creek Specter Tech compression cubes. Look for them on sale as they are a bit pricier than other brands and lines. I pack medium cubes with pants in one, shirts/tops in another. Small size cubes are perfect for underwear and socks. The thin fabric of the Specter Techs combined with the compression feature really work and if you fold the clothing (instead of rolling) you get few wrinkles.

You have to be careful about total weight as you can fit so much into each compression cube it can end up weighing more than packing in standard non-compression cubes.