DUmeter is a good one but not freeware
Having a quick search on the squinternet I found:
http://www.junell.com/docs/sw/bwmeter/bwmeter.zip
Would be nice if NTL provided something that we could use to ensure that we don't go over our allocate 1gb....As many threads will tell you though - Noone as yet seems to have been affected by the CAP. Question - Can NTL manage to monitor all the connections?