Antivirus products

I have avast anti-virus on my workstation and it works very well. http://avast.com/eng/avast_suite.html

Symantec is the best choice
managed updates (live update feature)
includes the fixs for any virus trojan or malicious activity involved with the network
Enterprise edition a must have

We've been using Computer Associates E-Trust AV for a number of years now (since V 4.5). Once installed, it basically takes care of itself. We use an admin server (and 3 distribution servers - for 350 computers) and have not had any virus problems since version 6.0 came out. Other than a few little problems here and there (which they all seem to have), it's been working flawlessly.

We use McAfee and have been VERY satisfied with the results. They detect more virus/trojans than any other virus scanner. We use the managed solution they have called Epolicy Orchestrator which updates, installs and gives you reports. They have a small business version that is less expensive and has the remote management capability. Norton did nothing for me but cause problems with all of the false positives and blue screens it causes. We have been using McAfee for over 5 years now and have not had one infection. The new version of Virusscan has buffer overflow protection which helps when someone is trying to exploit a Microsoft vulnerability. This version even has a anti spyware module that plugs right into Virusscan and it detects spyware that some of the others pass right up. If you want your problem solved, go McAfee..

First I have maintained several networks in the last six years. Ranging from 250+ PC's with 8 Servers to 1 Server and 25 PC's on a network.
I have used McAfee in a corporate environment for about 5 years at Diversified Plastics, it was very difficult to maintain, upgrades were expensive and time consuming.
I used Norton Enterprise for a little over a year at Life Mortgage, it worked well but quarantined too much, it should have cleaned or deleted more. Yes, I did properly set it up.
As for F-Prot Anti-Vir and AVG, I have had customers with more issues that caused constant (I am talking weekly to monthly) removal and reinstall of these products on a corporate level.
I have only used Computer Associates on peer-to-peer networks.
Since October I have been using NOD32 by ESET and I am currently transferring all my customers as their current subscriptions expire to NOD32. It is inexpensive compared to McAfee, Symantec and Computer Associates.
It was a little more difficult in the initial set up than Symantec but that was my first roll over and once I got the hang of it (the installation pattern needed) it was a breeze.
Now the negative, the updates, they are internet heavy. I solved this by having 1 server get the updates and then the clients grab the updates off the server. The second issue is that I either accidentally keep turning on Advanced Heuristics or it is set to come on by default but you must go in and turn them off for the e-mail otherwise anything with a PDF attachment takes 1 to 2 minutes to download. Turning this off (while keeping "normal? heuristics) is a simple removal of a check box.

Nod32 is a very excellent antivirus.I suggest this antivirus because this antivirus use very minimum Ram and their Powered by the ThreatSense? engine with advanced heuristics, which blocks far more unknown threats than the competition.Make your computer very secure bit per bit.win many award gold product.You can download nod32 here >Eset Product<
Nod32 also can offline update.it very good for who don't have internet connection.
NOD32 Offline Update for nod32 here =>>Eset Offline Update<

I have used Trend Micro on all of my client sites.

I use "Worry-Free Business Security ? Advanced" which is an 'all in one' package. They have CHARITY/NON-PROFIT pricing as well.

It has an Exchange scanner for antivirus and spam as well as a client scanner. Lower resources than Symantec, can do updates if clients are outside of the office and quite easy to confirm as it's all web-based.

That's just what we use.