There's two basic things that you'll need to do to protect your users from themselves. First is to have an anti- product of some sort. Be it antivirus, antispyware, or both. Second, you need to protect them from the crazy wide open internet that will get them in trouble if a customer sees 
As an absolutely free solution to the second problem, I've switched my dealer group to OpenDNS. All you have to do is point your DNS server to them, set up a bunch of settings, and then start blocking categories. Its really easy to get around, but no one has figured it out yet!
Soon I'll be going to a more robust solution that involves a real gateway/firewall that will monitor all connections made and smartly block the ones I don't want and track individual PC's usage. Costs a ton of money though. bleh.
On individual PC's I've been using Symantec's Endpoint Protection, but at $11 per person when buying it over a certain number (150 licenses?) its a bit steep and doesn't protect against everything. I might end up switching this next year to something that keeps up more on the spyware front.

As an absolutely free solution to the second problem, I've switched my dealer group to OpenDNS. All you have to do is point your DNS server to them, set up a bunch of settings, and then start blocking categories. Its really easy to get around, but no one has figured it out yet!
Soon I'll be going to a more robust solution that involves a real gateway/firewall that will monitor all connections made and smartly block the ones I don't want and track individual PC's usage. Costs a ton of money though. bleh.
On individual PC's I've been using Symantec's Endpoint Protection, but at $11 per person when buying it over a certain number (150 licenses?) its a bit steep and doesn't protect against everything. I might end up switching this next year to something that keeps up more on the spyware front.