2 things you could do:
1. set the computers that dont have internet to use a proxy server. With no proxy server available, internet fails. Or you could just not setup internet access at all on those computers.
2. setup the non-internet computers in their own address range and use a manged router to run an acl to block port 80 on that address range of computers.
I dont know of any hubs that can do any kind of blocking.
My Linksys router (BEFVP41 I think) can do that - you assign a specific IP address (not DHCP, but manually configured) and set the router's config page to filter those requests - they couldn't hit the internet.
so I'd say get a $50 broadband router (you don't need the one I have - I got it for vpn capability - the BEFSRwhatevernumbertheyareatnow is fine) and block those computer's IPs.