Winzip continues to function after the trial period expires too.

I haven't used it in a while, but by now it probably keeps track of past trial periods, though I couldn't say for sure. Whatever the case, you can' beat 7zip - it uses a superior compression algorithm and is capable of dealing with all other widely used algorithms too (ace, zip, rar, arj, etc.).

EDIT: And it's free, no trial period.