I try to recommend those products that have both Windows 95 and DOS versions. That way, end users can have the comfort of a Windows 95 interface to scan their files with, and power users have a small DOS-based product which can fit on a bootable floppy disk.
GFI MailSecurity is an email content checking, exploit detection, threats analysis and anti-virus solution that removes all types of email-borne threats before they can affect an organization’s email users.
Frisk Software are the makers of F-Prot, one of the older anti-virus scanners. These days, they have flavors for UNIX, BSD, Windows, and more! They also offer spam filtering services.
If there's an AV product that you feel should be mentioned, please e-mail me and I'll take a look at it. Representatives of any companies not on here are also welcome to contact me and ask for a listing.