Looking for a parental control website blocking software

Looking for some suggestions on website blocking software. I've heard of
Net Nanny and Cybersitter, but are there others out there, and are they
better? My basic requirements are that it be aware of Windows multiple
user accounts and setup different profiles based on the user account.
For example, that it remains completely inactive on a parental account,
but very intrusive in a kid's account.

Yousuf Khan