I've reviewed many security products, but it's rare for me to be so impressed with a product that I want to keep and use it after the review. Barracuda Networks' Spam Firewall is my favorite keeper so far this year.
In my experience, perimeter solutions usually rank just behind Internet-hosted service offerings in accuracy, with end-point solutions having the worst rates. This is not the case with Barracuda -- it's among the more accurate anti-spam products I've tested, even when compared with seemingly more intelligent hosted solutions. In a crowded field, Barracuda Spam Firewall stands out for being packed with features, easy to use, accurate, and relatively low-cost.