"Free" license for PKZip
Archive creation and encryption is fully supported. You wouldn't notice the missing features if the come-ons weren't so obvious. And if you do need those, you'll probably be looking at GNU Privacy Guard anyway.
One caveat: SecureZIP silently, presumptuously and immediately (when first run) takes over all file associations it knows about, including ZIP. WinZip users take note!WinZip 11.0 already offers most of this stuff, and it mentions digital signing (without showing you the grayed-out crippled buttons). On the other hand SecureZIP has snazzy modern icons.
I don't recommend any of this, of course. You need to keep track of passwords, to maintain access to your files. A touchy proposition, as the tickings and the tockings pile up, and your neurons quietly expire under the relentlessly calm assault of daily entropy. Personal encryption protocols become tedious very quickly, so unless you need this stuff, you're far better off to avoid it.