Space is important in what we do too, and that's why today I tracked down some of the most well known logos that use negative space, as well as some cool ones from companies you may not have heard of.
Two of the most well known are the USA Network logo and the FedEx logo. USA uses a stylized U and A to form an S between them. It's simple and obvious, much more so than FedEx's little secret. If you've never seen the arrow in the FedEx logo, (look between the E and the x) you'll never be able to unsee it now. It's an amazingly subtle and well executed addition, and I'm sure it has had a great effect for them. It takes their logo beyond simply being a mark for their company, and makes it a conversation point; you don't just pass a FedEx truck on the highway, you point out the logo to your friends and talk about how cool it is.
A now retired logo that is close to my heart is the former mark for the Big Ten athletic conference. Penn State joined the conference in 1993, bringing the total to 11 schools, and the logo was redesigned to reflect that. (notice the '11' between the G,T & E) The logo was redesigned again last year when Nebraska joined the conference, but instead of embracing the 12 universities they reverted to a stylized 10... which makes no sense at all.
Using negative space well isn't easy, and these examples are no exception. They manage to fit related characters and symbols into their logos without looking forced. They're simple, yet brilliant, and as a designer I get jealous every time I see them.
If you want more examples of great negative space usage in logos, you can see a nice collection here. Some of these may not be as famous, but they're just as impressive.