Cobion's OrangeBox Web is a very similar product to DynaComm i:filter. Designed to integrate with a proxy server (for example, Microsoft ISA on Windows 2000/XP), it is also happy to sit on a number of popular Linux and Unix platforms. It can also be used as a proxy server in its own right if you have a small or medium-sized intranet network.
SurfControl has long been a name in internet security, with its CyberPatrol product one of the best known applications for home use, and its Web Filter application is an excellent business tool for micro-managing users' access to the internet.
Symantec Web Security is a product specifically designed to monitor the content of HTTP, HTTPS and FTP traffic. It takes the form of a proxy server that sits behind your firewall; with most firewalls it will operate transparently, but you have the bonus of integration with Check Point's FireWall-1.