If you have to decompress files regularly, especially image files, you may find Zipeg interesting. It's definitely one of the nicest image decompressors we've used in a while.
The key feature of Zipeg is a cool preview function which allows you to see what you are going to decompress before you do it. This is great if you can't remember what's in a file or are suspicious about its contents. Zipeg supports a huge variety of archive formats including: ZIP, RAR, ARJ, LHA/LZH, 7z, TAR, GZ, TGZ, BZIP2, CPIO, RPM, ISO, CHM, Z, CBR, CBZ, WAR and EAR.
You can extract/unzip items in Zipeg simply by dragging them and the interface is remarkably easy to use and good looking. It can process archives in the background whilst you work, sorts content of folders by name, size or date and automatically checks for the latest updates.
This is one of the best image compression utilities out there although the thumbnails can take some time to appear when you select a file.