South Dakota and Oregon have had county based sex offender lookups that are now integrated into their statewide sex offender registries. Each are online at their state sites and at the National Sex Offender Public Registry operated by DOJ. The DOJ site also includes searches in the District of Columbia and the territory of Guam.
The Ohio legislature is entertaining a bill that would establish a civil registry of child sexual abusers.
A recent Missouri Supreme Court decision will require that sex offenders convicted of crimes prior to 1995 be removed from the sex offender registry. Read the story