Simple handling of compressed archives is a breeze on a Mac, simply secondary-click and hit "Compress". Likewise opening a zip file is as easy as a double-click. But what happens when you want to get a bit more advanced with your compression archives? That's where something like iZip Archiver steps in.
iZip Archiver is available from both the Mac App Store and directly from the developer's site. The version available in the Mac App Store is a fairly limited application, but the free version available from izip.com allows you to do a couple of things that your Mac can't do natively, even with the likes of The Unarchiver, TinyExpander or Stuffit Expander installed.
Essentially iZip Archiver will allow you to create archives in .zip format, secure them with a passcode and share them via files.com. That bit of the app doesn't really add anything to the default Mac-archiving experience. But what it will do is allow you to open and edit archives without extracting them first.
Opening an archive mounts it like an external drive or .dmg, and allows you to look through the contents, open, edit, rename or extract single files, as well as add to or delete items from the archive. In this way you can add files you'd forgotten to zip up, or remove files you no longer want in your archive without having to unzip and re-zip them. For small archives it only saves a little time, but for really massive archives, skipping the extraction step will save you heaps of time. iZip Archiver supports ZIP, ZIPX, RAR, TAR, TAR.GZ and 7ZIP files, so most common archives are covered.
There are other alternatives like BetterZip 2 and Stuffit Deluxe to name just two, but most of them aren't free. So if you're looking for a free tool for the occasional archive modification, iZip Archiver will do the job for you for nothing. The restricted iZip Archiver is available from the Mac App Store, while the more fully featured version is available directly from the developer's site.