Thanks to a suggestion from Bryan Veloso this weekend, I started using The Unarchiver, a small yet capable archive unpacker. It was designed to be a replacement for OS X's BOMArchiveHelper.app and The Unarchiver exceeds what that could ever do, including support for Zip, Tar-GZip, Tar-BZip2, Rar, 7-zip, LhA, StuffIt and just about any other format you can get your hands on. Oh and it's free (as in WordPress). Before The Unarchiver came around, I was pretty much limited to using the inferior UnRarX.
However, as the name implies, it only unarchives packages. If you want to create tarballs and other such files, you might opt for MacItBetter's BetterZip. While it's not free, it retains the GUI experience and keeps you from getting your hands dirty with commands like "tar cvzf file.tar.gz filedir".