Mac OS X has had a zip utility built into it for some time. For extracting stuff other than Zip files, the Unarchiver's your friend. But what about actually compressing and managing archives? That's where BetterZip 2 steps in.
BetterZip 2 allows you to open archives without first extracting them, allowing you to see precisely what's inside them before processing them. Often you've got loads of files compressed together, but you only want one -- BetterZip allows you to extract single files from archives without having to extract the whole lot, which can save you time and disk space if it's a really large archive.
You can also update archives, adding files into an already compressed archive without having to extract the whole lot first and then re-compressing them together.
BetterZip is able to open and extract most common formats, from ZIP to TAR, RAR to JAR, it's got you covered (for a full list see the MAS listing). BetterZip can also compress files into six archive types natively (ZIP, TAR, GZip or BZip2 compressed TAR, XAR and 7-Zip), as well as RAR archives courtesy of an external RAR command-line utility. You can also secure your ZIP, 7-Zip and RAR files with passwords, with WinZip compatible AES-256 encrypted archives at your fingertips.
The US$19.99 BetterZip brings a full archive manager to your Mac. It's fast, easy to use and handles all but the most obscure archives. I would like to see the ability to create a few more archive types, but native ZIP and 7-Zip support will see you though most of your archiving needs.