Most states have online searches for inmates through their Department of Corrections websites. Here is the complete list (also includes county jail rosters and recent arrests) - Inmate Locator.
The California Department of Corrections recently placed their inmate locator online. What's great about this site is that you cannot only search by inmate number, you can search by last name.
Vinelink.com is another database that provides inmate information at the state and county level for most states. Vinelink is the online version of VINE (Victim Information and Notification Everyday), the National Victim Notification Network. This service allows crime victims to obtain timely and reliable information about criminal cases and the custody status of offenders 24 hours a day.
If the county or state department of corrections you are searching for does not have an inmate locator on the web, I suggest you call the prison directly. They will tell you if the inmate you are looking for is incarcerated in their facility.
Localcrimenews.com is a new site that provides the most recent arrest reports from many different government sources throughout California. The site covers arrest records for Los Angeles, San Diego, Sacramento, Fresno, San Jose, Bakersfield, Stockton, San Bernardino, Riverside and the City of Long Beach. The arrest records include the name and address of the person arrested, the crime report number, the arrest date, the charges and sometimes even the bail amount.
Whosarrested.com is another site that lists arrest records for Las Vegas, Miami, Reno, Tampa and Phoenix. WhosArrested.com claims they obtain their information from government sources. Unlike Crimenews.com, Whosarrested.com has a searchable database of inmate arrest records comprised of all arrests resulting in detention as reported by city and county institutions since January 1st, 2009. The criminal records include mug shots, initial charges, bail amounts, identity information and news.
Contrary to the belief that arrest records are not public records, you can clearly see there are sites that provide recent arrest record information from major metropolitan areas throughout the United States. However, it is important to remember that arrest records of anyone under the age of 18 are not public and remain confidential.