SearchEnable is a new jailbreak tweak that allows you to add alternative search engines to Safari. The tweak adds Ask, Baidu, blekko, Sogu, Volunia, Yandex, Evi and WolframAplha to the Safari search engine options listed under Settings. SearchEnable basically gives you a few more international choices besides the popular U.S. options (Google, Yahoo and Bing) already included on your phone. Make sure you have the Safari app enabled under SBSettings or the Safari setting panel will not be available.
SearchEnable is available for free in Cydia via the ModMyi repo.