I would like to reopen https://serverfault.com/questions/381599/monitoring-work-users-and-their-network-habbits question as I believe it should be allowed to ask for specific scenario question. I think multiple people/work places can benefit from this as it's something very common nowadays (blocking facebook etc). The question is very specific and one "GOOGLE -> software to stop workers accessing facebook" line won't cover it. I do agree software does change but that's why answers / questions can be updated/edited and more answers can be provided with time. The question doesn't ask about price range or what is better but simply asks for software / solutions that can help. Answers don't nessecary need to be software related. It could be said that one should introduce proper GPO allowing or disallowing some websites.
The practice of implementing blocks in the workplace is very common, but the choice of the software to do so is not really a topic we can help you with. There are lots of options out there (rigging your DNS server to say
NXDOMAIN for facebook.com, blocking their IP blocks on your firewall, installing Websense or another kind of content filter, etc.) - you need to do the research on each one.
If you were asking "I have Websense installed, how do I make it do X?", or "How can I block Facebook using OpenBSD's
pf firewall?" that would be on-topic, but what you're asking for us to do is recommend software based on requirements we can't know. That in and of itself is bad, but when combined with Jeff's analysis of why questions about product/service recommendations are bad it creates a question that we can't reasonably answer in a way that will have lasting value.
I'm just one guy though - there may be other opinions.
The Stackexchange software works badly for polls and lists of things. As your question is asked right now people are just going to provide links to various products. This will not be very useful. It doesn't encourage people to add any useful information, that isn't already documented elsewhere.
In stead of asking for a list of things, you should see if you can modify your question to ask, how do I evaluate the list of things.
A question like 'I am currently looking for content filtering software, what features and functionality should I be looking for for when I evaluate the various solutions.' is more likely to be left open, and will probably be just as useful when combined with the lists you can get from Wikipedia, and search engine results.
Here is an example for switches. The 'what features/how do you evaluate' style question still will result in a fair amount of answers, but they will be more useful in the long term, and will not encourage vendors, to spam the site recommending their products.