Want to know what the world is talking about right now? Looking for a juicy search term? Need to kill a few hours? Then check out these powerful social search engines:

Bottlenose

A real-time social intelligence engine that analyzes activity across all the major social networks. Bottlenose’s fancy algorithm, called “StreamSense,” uses in-house natural-language processing, personalization and semantic techniques to figure out trending topics and trending content.

Their never ending sea of updates is called a “stream,” and gives users a comprehensive overview of top links (including newspaper articles), recent posts, trending topics, trending images and recent comments for any given search term. You can even check out trending people, which is great for connecting similarly-minded folks.

Bottlenose launched its public beta form in May 2012. Since then, it has fielded 3 acquisition offers (including one suspected offer from Twitter) and scored nearly $1 million in financing from ff Venture Capital and Prosper Capital.

Topsy

A conversation search engine that lets you explore top links, tweets, photos, videos and “experts.” You can instantly see the number of mentions—by the minute, hour or day—for any term, phrase, username link or hashtag. Topsy also features a special influence algorithm that displays the most pertinent and popular social results, but the real gem is the social analytics tool that lets you visually compare up to 3 queries.

As a testament to their powerful social analytics, Topsy expects to index and measure approximately 250 billion items by the end of 2012, with over 16 trillion pre-computed metrics.

Social Mention

A simple, easy-to-use tool that measures over 100 social media properties directly, including Twitter, Facebook, FriendFeed, YouTube, Digg, Google etc. View top keywords, top users, top hashtags, sources, reach and even sentiment (positive, neutral, negative).

Social Mention is pretty basic, but it does dive into some deeper measurements:

Strength: The likelihood that your brand is being discussed in social media
Sentiment: The ratio of mentions that are generally positive to those that are generally negative
Passion: A measure of the likelihood that individuals talking about your brand will do so repeatedly
Reach: A measure of the range of influence