HistoryPin is a Google Maps mashup that allows visitors to pin historic photos on a map and to view photos across locations and dates. The site offers a video introduction and tours of some of the best content. For more details on using the site, read The Internet Patrol.

A recent, high profile murder trial in Florida used search history to incriminate the plaintiff. Just how much of your history actually remains on your personal computer? Leo Notenboom, of Ask-Leo.com, explains that unless you have spyware installed on your computer, your every keystroke is not being recorded. However, there is a fair amount of history that is available. He also reviews various programs and how useful they are at removing some of that history.

Gmail account almost full? Anne Mitchell of The Internet Patrol explains how to free lots of space by deleting old attachments. On the other hand, you can always simply buy more storage space from Google. 20GB costs just $5.00 a year.

To help you keep your Gmail account secure, Gmail lists recent sessions at the bottom of your inbox. There you can view recent account activity, and also see if your Gmail account is still logged in another session. If you do see another open session (maybe its simply your laptop?) there is a link to log out of the remote session.

Identifying a mystery celebrity in a photo, or finding websites that have stolen your copyrighted images has gotten a whole lot easier with Google’s Search by Image. Images can be dragged and dropped, uploaded, specified by URL, or (with a Chrome or Firefox extension) simply right-clicked. To see Dave Taylor ID a mysterious blonde, read Can I Identify a Photo Using Image Search?.

What do you love? Google thinks it knows, and has launched a new search service by the same name. Searching for “cats” for example, will display results in a visual table format from multiple Google services, including YouTube, Google Maps, Blog Search, Calendar, Patent Search, Picasa, Books, Image Search, Translate and SketchUp. Maybe it’s useful. Maybe it’s just a toy. What do you think?

In a move designed to make Google more social, the search giant recently added a voting widget to both its search results and third-party websites. Called Google Plus One, it allows those signed into their Google accounts to vote their approval of web pages. Pages you vote for will display in your Google account profile, unless you choose to make them private. For pictures and a more detailed explanation, read Leo Notenboom’s What’s that “+1″ Thing?.

Just recently released from beta, Fring is Google’s free group video call app for iPhone and Android. The mobile phone app enables group video phone calls with up to four people at once, over Wifi or 3G/4G phone connections. It also allows plain-old audio talk and has a text chat mode. It even allows you to call regular phone numbers for rates starting at a penny a minute.

Because our online accounts have become so important, both Google/Gmail and Facebook now offer two-step verification for enhanced security. The basic concept in two-step security is that in addition to your username and password, whenever you login into a new machine/browser you will verify your identity with a single use verification code that is sent to your phone. For details on the Google system, read this support article. Facebook just started rolling out their two-factor authentication this week. Learn more with the Lifehacker article.

Recently Google announced a daily trivia game called A Google a Day. Unlike other trivia games, where it is considered cheating to “google” the answer, this daily quiz encourages it! But in order to squelch answers from other players appearing in the search results, A Google a Day uses a special version of Google that is a snapshot of the previous day’s database. Like newspaper crossword puzzles, the difficulty of the trivia questions increases as the week progresses from Monday.