Do you mean purely "open" them, rather than "install" them? A .deb file is a packaged software installer for Debian Linux (and its derivatives.) If you want to install it, you're out of luck, I don't know of any way to install .deb packages on OS X.
If all you want to do is expand the package to look inside, try dpkg-deb, specifically the -x command-line option.
Don't worry I found an application that did it for me! Thanks anyway.
what's the program you are using?Don't worry I found an application that did it for me! Thanks anyway.