The latest SecureZIP for Windows release retains the ZIP utility features you'd expect, while adding high-end encryption and public/private key cryptography via its own key directory (in partnership with authentication company Comodo Group.)
One of the things I've always liked about PKWare is that they don't forget what brought users to them in the first place, which was (and is) in most cases its ZIP technology.
While the addition of high-security encryption is the keu point here, take a look at how the new release integrates with Office, automatically zipping Outlook attachments; if your recipient is running SecureZIP, encryption/decryption is equally automatic (per your instructions/options-selections is setup.)
The next revision, expected later this summer, should make the auto zip/encrypt features available to Outlook Express and WindowsMail users.
At a starting price of $39.95 for commercial users -- free for home use -- this one's worth a hard look, especially so in hard times which include higher threats every day.
An evaluation copy can be downloaded here.