If you ever recieved a mail with a bigger attachment from me, you might have noticed that I am usually choosing 7zip
to compress it. 7-zip is a great file archiver just like ZIP or RAR, but it has several advantages: It has a better compression ratio, usually my .7z files are half as big as .zip files, depending on the type of their content. With the usual combination of source code files, binaries and some images, I'm usually getting excellent compression results. 7-Zip uses an optional very secure encryption method (AES), supports huge file sizes, and best: It is open source and free.
In addition it is able to compress into other file formats (ZIP, GZIP, BZIP2 and TAR) and decompress even more (RAR, CAB, ISO, ARJ, LZH, CHM, Z, CPIO, RPM, DEB and NSIS). Simply a great piece of software.