With services like StumbleUpon becoming ever more popular, Google has decided to throw its hat into the ring. On Wednesday, the company added a feature to its toolbar that recommends Web sites based on past search history.

The company has been offering the capability to keep track of past searches since June 2005, integrating the functionality across several of its products. However, it was billed as mostly a feature to help improve future search queries.

Now, that data will be used to recommend new sites that Google customers have not seen based on their past searches. Google says this is meant to allow its users to discover information without typing in a query.

The new feature appears as a pair of dice on the toolbar. "Click on the dice, and we'll take you to a site that may be interesting to you based on your past searches," personalization lead engineer Sep Kamvar said.

50 sites will be available each day, and users must upgrade to the most recent version of the Google Toolbar in order to take advantage of the new feature.

In addition, the company will release a version of the feature aimed at those using its personalized homepage functionality. The tab will be refreshed once daily with new recommendations.

Google's announcement comes amid rumors of a possible acquisition of StumbleUpon by auction site eBay. Both TechCrunch and GigOm reported Wednesday that the company had signed a definitive agreement worth at least $40 million.

"By marrying the [StumbleUpon] toolbar to Skype client, eBay can do an end run around Google's dominance of the search business," Om Malik said of the possible deal. "Skype has been slowly integrating various different services into its client, and slowly becoming eBay's desktop backdoor."

Neither eBay nor StumbleUpon were publicly commenting on the reports.