7-Zip is an open source Windows archive manager that can handle the following formats: 7z, GZIP, BZIP2, ZIP, TAR, and some other formats. Under Linux, you can use instead p7zip to extract the content of archive files having the '7z' format.
To install p7zip on Ubuntu (10.04/10.10/11.04), launch the terminal and issue this command:
sudo apt-get install p7zip p7zip-full
After installing this command line utility, you can extract 7z files with this command:
7z x file.7z
Replace file.7z with the name of your archive file.