mgzip is a program that makes use of SMP machines and zlib to use as many processors as you have to quickly compress files into gzip compatible format. mgzip only compresses; gunzip must be used to uncompress the resultant file. I have been able to compress files three times faster than standard gzip on a 4 processor Alpha 4100 using three worker threads. Currently, mgzip will compile and run on Digital Unix 4.0[BD], Linux with a suitable pthread library, and AIX 4.3. Porting to other Unices with pthread libraries should be an easy task, and may be as simple as compiling.

http://www.lemley.net/mgzip.html