Stuffit Deluxe 7? (released)
Aladdin Systems is rumored to released Stuffit Deluxe 7.0 for the Macintosh very soon.
Stuffit Deluxe is currently at version 7.5 for Windows, and 6.5 for the Macintosh. The new versions is reported to improve compression up to 30%.
Update: Stuffit 7.0 released
The new StuffIt X(TM) (pronounced "ex"), file format integrates compression with security and safety options to meet the requirements of business and today's digital lifestyle. The StuffIt X, or .sitx, file format provides stronger encryption (512 bit), improved compression (up to 30% over other formats), error-correction, larger archive size, and support for long-file names.