Twing: search engine for forum posts
If you follow any forum regularly, Twing could be useful to you. You can narrow your search down to one message board, which might make a good substitute if the built-in search is faulty in your community of choice. Another promising feature is the ability to sign up for an account to keep tabs on the threads you're following.
Even if you're not active on a forum, Twing has some interesting tools for tracking the hottest links and conversations. Most popular links, threads, and forums are all ranked, and RSS feeds are available for each. Twing says that the most popular thread on the Internet right now is called "longest ever thread." While we don't doubt this is accurate, we'll leave it up to you to decide how practical you find it.