We started with the firefox addon "Kidzui". But we dropped it once the older two were both getting frustrated that it didn't allow access to educational websites for older kids because they were not on the "acceptable" list. I am sure that it would have been updated somewhat by now, and may be worth your checking it out.
We don't use anything on their laptops now, and they have been instructed to close browser windows immediately or call us if anything funny pops up at all, including anything that looks nothing like their intended search or anything that makes them go "huh???".
It seems to be working. They also each have a small A6 notebook next to their laptops so that they can come ask us to confirm spelling when they are searching. It helps to eliminate some dodgy search results.
The obvious is also to set your browser security settings to their strongest, keep all PC's in rooms where everyone can see them and explain the rules about chatting online. My kids are not allowed to install new games without one of us checking them out first, and if there is live chat we disable it unless it's something like LAN games or co-operative games with people they know.
Aiden is starting to ask why and we have had long chats about what is safe or not safe to divulge online to anyone: eg. no sharing of full name, address, telephone numbers, age, info on his brothers, no sharing of pictures via internet programs or sites (only e-mails - which is fine cause I am copied on any and all mails he sends and receives).
Ummm I can;t think of anything else off the top of my head.
