7Zip

Download: 7Zip
Purpose: Multitalented (un)zipper
Platforms: Windows 7, Vista, XP; Windows Server 2008, 2003; available in 64-bit
Cost: Free

Another venerable Windows utility, 7Zip still rates as a must-have, even though Windows supports the ZIP format natively.

Why? Because some people of the Apple persuasion will send you RAR files from time to time, and 7Zip is the fast, easy, completely free way to handle them.

7Zip also creates self-extracting EXE files, which can come in handy (although heaven help you if you ever try to email one -- most email scanners won't let an EXE file through), and it supports AES-256 bit encryption. The interface rates as clunky by modern standards (see screenshot below), but it gets the job done with ZIP, RAR, CAB, ARJ, TAR, 7z, and many lesser-known formats. It even lets you extract files from ISO CD images.

A poster boy for the open source community, 7Zip goes in easily, never nags, and wouldn't dream of dropping an unwanted toolbar on your system. Call it enlightened.

7Zip makes it easy to work with RAR files, one of the few compressed formats (other than ZIP) that's still widely used.