This is the official 7zip webpage. While there are a few perfectly fine file archivers out there, I prefer 7zip because it is open source. Tested, tried and trued by people all over the world. Popular open source applications tend to be the safest and, just as importantly, most PRIVATE software you can download.
No corporations trying to sneak in trackers or ads. No pop ups reminding you that your license has expired (not that anything is wrong with that in and of itself). 7-Zip does it all.
Houses a great solution to my compression/decompression needs in 7zip. Also supports a very secure file encryption via compressing the files in question, which incidentally I currently have a difficult time remembering the password for, effectively locking me out of my older files. Huhu
Excellent archiving utility for Windows, there are also packages for linux available from distros' own repositories, and it's open source, of course.
7z is one of the most efficient compression mechanisms geared towards everyday users, beating eg. Zip-archives in nearly every category. 7-Zip also supports other most popular archives' decompression, and compresses 7z, zip, bz2, tgz etc., usually better than the "original" compression utility. It does not support compressing rars, but decompresses them too.
Light, clean and easily navigated site, and the forums at sourceforge.net provide You with developer-answered help and support.
Best archiving & extraction tool out there! Open-source, free, safe, quick, low memory consumption, very very easy to use, and just awesome in every way!!!!
The site is awesome, too. You can't go wrong with 7zip!
Stay away from 7-zip.com though! It's a scam site!